Well, I've tried this :
# systemctl stop webmin
# systemctl status webmin
● webmin.service - LSB: web-based administration interface for Unix systems
Loaded: loaded (/etc/init.d/webmin; generated)
Active: inactive (dead) since Sun 2021-08-22 15:12:09 CEST; 11s ago
Docs: man:systemd-sysv-generator(8)
Process: 1021 ExecStart=/etc/init.d/webmin start (code=exited, status=0/SUCCESS)
Process: 5623 ExecStop=/etc/init.d/webmin stop (code=exited, status=0/SUCCESS)
CPU: 14.270s
Aug 21 19:50:13 discovery systemd[1]: Starting LSB: web-based administration interface for Unix systems...
Aug 21 19:50:14 discovery perl[1023]: pam_unix(webmin:auth): authentication failure; logname= uid=0 euid=0 tty= ruser= rhost= user=root
Aug 21 19:50:16 discovery webmin[1023]: Webmin starting
Aug 21 19:50:17 discovery systemd[1]: Started LSB: web-based administration interface for Unix systems.
Aug 22 15:12:09 discovery systemd[1]: Stopping LSB: web-based administration interface for Unix systems...
Aug 22 15:12:09 discovery webmin[5624]: Stopping Webmin server in /usr/share/webmin
Aug 22 15:12:09 discovery systemd[1]: webmin.service: Succeeded.
Aug 22 15:12:09 discovery systemd[1]: Stopped LSB: web-based administration interface for Unix systems.
Aug 22 15:12:09 discovery systemd[1]: webmin.service: Consumed 14.270s CPU time.
# apt update
Hit:1
http://deb.debian.org/debian bullseye InRelease
Get:2
http://deb.debian.org/debian-security bullseye-security InRelease [44.1 kB]
Get:3
http://ftp.debian.org/debian bullseye-backports InRelease [39.3 kB]
Get:4
http://deb.debian.org/debian bullseye-updates InRelease [36.8 kB]
Ign:5
https://download.webmin.com/download/repository sarge InRelease
Hit:6
https://download.webmin.com/download/repository sarge Release
Fetched 120 kB in 1s (135 kB/s)
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
2 packages can be upgraded. Run 'apt list --upgradable' to see them.
# apt upgrade
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Calculating upgrade... Done
The following packages have been kept back:
guile-2.2-libs libobjc4
0 upgraded, 0 newly installed, 0 to remove and 2 not upgraded.
NOTE : this two components are still not upgradable

grrr.
lets continue :
# apt list proftpd*
Listing... Done
proftpd-basic/stable,now 1.3.7a+dfsg-12 all [residual-config]
proftpd-core/stable 1.3.7a+dfsg-12 amd64
proftpd-dev/stable 1.3.7a+dfsg-12 amd64
proftpd-doc/stable 1.3.7a+dfsg-12 all
proftpd-mod-autohost/stable 0.6-1+b1 amd64
proftpd-mod-case/stable 0.7+git73896501cf-2+b1 amd64
proftpd-mod-clamav/stable 0.14~rc2-4 amd64
proftpd-mod-counter/stable 0.6.2-2 amd64
proftpd-mod-crypto/stable 1.3.7a+dfsg-12 amd64
proftpd-mod-fsync/stable 0.3-3+b1 amd64
proftpd-mod-geoip2/stable 0.1-1+b2 amd64
proftpd-mod-geoip/stable 1.3.7a+dfsg-12 amd64
proftpd-mod-ldap/stable 1.3.7a+dfsg-12 amd64
proftpd-mod-msg/stable 0.5-3 amd64
proftpd-mod-mysql/stable 1.3.7a+dfsg-12 amd64
proftpd-mod-odbc/stable 1.3.7a+dfsg-12 amd64
proftpd-mod-pgsql/stable 1.3.7a+dfsg-12 amd64
proftpd-mod-proxy/stable 0.7-1+b1 amd64
proftpd-mod-snmp/stable 1.3.7a+dfsg-12 amd64
proftpd-mod-sqlite/stable 1.3.7a+dfsg-12 amd64
proftpd-mod-statsd/stable 0.1-1+b2 amd64
proftpd-mod-tar/stable 0.4-2 amd64
proftpd-mod-vroot/stable 0.9.8-4+b1 amd64
proftpd-mod-wrap/stable 1.3.7a+dfsg-12 amd64
# apt install proftpd
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Note, selecting 'proftpd-core' instead of 'proftpd'
The following additional packages will be installed:
libhiredis0.14 libmemcached11 libmemcachedutil2 proftpd-doc
Suggested packages:
openbsd-inetd | inet-superserver proftpd-mod-ldap proftpd-mod-mysql proftpd-mod-odbc proftpd-mod-pgsql proftpd-mod-sqlite
proftpd-mod-geoip proftpd-mod-snmp proftpd-mod-crypto proftpd-mod-wrap
The following NEW packages will be installed:
libhiredis0.14 libmemcached11 libmemcachedutil2 proftpd-core proftpd-doc
0 upgraded, 5 newly installed, 0 to remove and 2 not upgraded.
Need to get 4,425 kB of archives.
After this operation, 9,210 kB of additional disk space will be used.
Do you want to continue? [Y/n] n
Abort.
NOTE : trying to install proftpd-core has always failed till now since the bullseye upgrade, so let's try to install proftpd-basic instead :
# apt install proftpd-basic
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
The following additional packages will be installed:
libhiredis0.14 libmemcached11 libmemcachedutil2 proftpd-core proftpd-doc proftpd-mod-crypto proftpd-mod-wrap
Suggested packages:
openbsd-inetd | inet-superserver proftpd-mod-ldap proftpd-mod-mysql proftpd-mod-odbc proftpd-mod-pgsql proftpd-mod-sqlite
proftpd-mod-geoip proftpd-mod-snmp
The following NEW packages will be installed:
libhiredis0.14 libmemcached11 libmemcachedutil2 proftpd-basic proftpd-core proftpd-doc proftpd-mod-crypto proftpd-mod-wrap
0 upgraded, 8 newly installed, 0 to remove and 2 not upgraded.
Need to get 6,204 kB of archives.
After this operation, 11.7 MB of additional disk space will be used.
Do you want to continue? [Y/n]
Get:1
http://deb.debian.org/debian bullseye/main amd64 libhiredis0.14 amd64 0.14.1-1 [35.5 kB]
Get:2
http://deb.debian.org/debian bullseye/main amd64 libmemcached11 amd64 1.0.18-4.2 [94.5 kB]
Get:3
http://deb.debian.org/debian bullseye/main amd64 libmemcachedutil2 amd64 1.0.18-4.2 [22.3 kB]
Get:4
http://deb.debian.org/debian bullseye/main amd64 proftpd-core amd64 1.3.7a+dfsg-12 [2,577 kB]
Get:5
http://deb.debian.org/debian bullseye/main amd64 proftpd-mod-wrap amd64 1.3.7a+dfsg-12 [498 kB]
Get:6
http://deb.debian.org/debian bullseye/main amd64 proftpd-mod-crypto amd64 1.3.7a+dfsg-12 [790 kB]
Get:7
http://deb.debian.org/debian bullseye/main amd64 proftpd-basic all 1.3.7a+dfsg-12 [492 kB]
Get:8
http://deb.debian.org/debian bullseye/main amd64 proftpd-doc all 1.3.7a+dfsg-12 [1,695 kB]
Fetched 6,204 kB in 0s (49.4 MB/s)
Selecting previously unselected package libhiredis0.14:amd64.
(Reading database ... 98931 files and directories currently installed.)
Preparing to unpack .../0-libhiredis0.14_0.14.1-1_amd64.deb ...
Unpacking libhiredis0.14:amd64 (0.14.1-1) ...
Selecting previously unselected package libmemcached11:amd64.
Preparing to unpack .../1-libmemcached11_1.0.18-4.2_amd64.deb ...
Unpacking libmemcached11:amd64 (1.0.18-4.2) ...
Selecting previously unselected package libmemcachedutil2:amd64.
Preparing to unpack .../2-libmemcachedutil2_1.0.18-4.2_amd64.deb ...
Unpacking libmemcachedutil2:amd64 (1.0.18-4.2) ...
Selecting previously unselected package proftpd-core.
Preparing to unpack .../3-proftpd-core_1.3.7a+dfsg-12_amd64.deb ...
Unpacking proftpd-core (1.3.7a+dfsg-12) ...
Selecting previously unselected package proftpd-mod-wrap.
Preparing to unpack .../4-proftpd-mod-wrap_1.3.7a+dfsg-12_amd64.deb ...
Unpacking proftpd-mod-wrap (1.3.7a+dfsg-12) ...
Selecting previously unselected package proftpd-mod-crypto.
Preparing to unpack .../5-proftpd-mod-crypto_1.3.7a+dfsg-12_amd64.deb ...
Unpacking proftpd-mod-crypto (1.3.7a+dfsg-12) ...
Selecting previously unselected package proftpd-basic.
Preparing to unpack .../6-proftpd-basic_1.3.7a+dfsg-12_all.deb ...
Unpacking proftpd-basic (1.3.7a+dfsg-12) ...
Selecting previously unselected package proftpd-doc.
Preparing to unpack .../7-proftpd-doc_1.3.7a+dfsg-12_all.deb ...
Unpacking proftpd-doc (1.3.7a+dfsg-12) ...
Setting up proftpd-doc (1.3.7a+dfsg-12) ...
Setting up libmemcached11:amd64 (1.0.18-4.2) ...
Setting up libhiredis0.14:amd64 (0.14.1-1) ...
Setting up libmemcachedutil2:amd64 (1.0.18-4.2) ...
Setting up proftpd-core (1.3.7a+dfsg-12) ...
Adding system user `proftpd' (UID 108) ...
Adding new user `proftpd' (UID 108) with group `nogroup' ...
Not creating home directory `/run/proftpd'.
Adding system user `ftp' (UID 109) ...
Adding new user `ftp' (UID 109) with group `nogroup' ...
Creating home directory `/srv/ftp' ...
'/usr/share/proftpd/templates/welcome.msg' -> '/srv/ftp/welcome.msg.proftpd-new'
Synchronizing state of proftpd.service with SysV service script with /lib/systemd/systemd-sysv-install.
Executing: /lib/systemd/systemd-sysv-install enable proftpd
Setting up proftpd-mod-crypto (1.3.7a+dfsg-12) ...
Setting up proftpd-mod-wrap (1.3.7a+dfsg-12) ...
Setting up proftpd-basic (1.3.7a+dfsg-12) ...
Processing triggers for man-db (2.9.4-2) ...
Processing triggers for libc-bin (2.31-13) ...
NOTE : Bingo ! that was proftpd-basic that needed to be installed
# apt upgrade
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Calculating upgrade... Done
The following packages have been kept back:
guile-2.2-libs libobjc4
0 upgraded, 0 newly installed, 0 to remove and 2 not upgraded.
NOTE : btw, these two still refuse to be upgraded !
let's see why :
# apt list guile*
Listing... Done
guile-2.2-dev/stable 2.2.7+1-6 amd64
guile-2.2-doc/stable 2.2.7+1-6 all
guile-2.2-libs/stable 2.2.7+1-6 amd64 [upgradable from: 2.2.4+1-2+deb10u1]
guile-2.2/stable 2.2.7+1-6 amd64
guile-3.0-dev/stable 3.0.5-4 amd64
guile-3.0-doc/stable 3.0.5-4 all
guile-3.0-libs/stable 3.0.5-4 amd64
guile-3.0/stable 3.0.5-4 amd64
guile-bytestructures/stable 1.0.7-3 amd64
guile-cairo-dev/stable 1.11.2-3 amd64
guile-cairo/stable 1.11.2-3 amd64
guile-g-wrap/stable 1.9.15-3.1 amd64
guile-gcrypt/stable 0.3.0-3 amd64
guile-git/stable 0.4.0-3 amd64
guile-gnome2-dev/stable 2.16.5-2+b2 amd64
guile-gnome2-glib/stable 2.16.5-2+b2 amd64
guile-gnome2-gtk/stable 2.16.5-2+b2 amd64
guile-gnutls/stable 3.7.1-5 amd64
guile-json/stable 4.3.2-2 amd64
guile-library/stable 0.2.6.1-2 amd64
guile-lzlib/stable 0.0.2-2 amd64
guile-sqlite3/stable 0.1.3-2 amd64
guile-ssh/stable 0.13.1-4 amd64
guile-zlib/stable 0.0.1-3 amd64
guile-zstd/stable 0.1.1-2 amd64
NOTE : ah ? there is a 3.0 version is this why it can't be upgraded ?
what should I do ?
- I can't just deinstall it and install the v3.0 version so what do you suggest ?
for the second one, libojc4 it is currently installed in version 8.3.0-6 and upgradable to 10.2.1-6 amd64...
there was no new version between the 8.3 and 10.2 ??? answer there was : stable 9.3.0-22 amd64...
so why this one never been upgraded and 8.3 still installed and not upgradable ???