automatic boot on PXE after sid installation

[AoiHana]

Hello.

I'm not new with linux nor debian and usually I can work my way around myself, as long as I'm the source of the problem.
I installed debian sid through a netinst (64b amd64, the computer is B50-10), checked the usb stick image integrity, it was fine, then went along with the installation, choosing LVM for partitioning, then MATE for desktop.
Rebooted, and it could only (try to) boot though PXE when the cable was on, or reboot endlessly if it was off.
I can't even access the BIOS, the PXE menu is almost immediate, what the heck with that for god's sake ?! I never met a computer like this.
It has seemingly mandatory "EFI": couldn't assign the "label" in the partitioning menu to any partition, nor could remove it from the EFI partition which was the first on the disk after a 1 Mo empty one. Very nice
I had debian on this computer before, and I never had that PXE stuff going on, which is a nonsense.
The only hypothese I can bring on, is that the installation program messed up with that EFI partition in a way it shouldn't have ?

Now how do I access the BIOS ?
In the meantime I'm trying Mint, but being based on debian, there's a chance it will end up the same.

Thanks for your help.

[Head_on_a_Stick]

Now how do I access the BIOS ?

https://www.dtonias.com/lenovo-b50-laptop-enter-bios-boot-menu/?

It would have been quicker to ask a search engine yourself instead of getting me to do it for you.

If you have already tried that then please explain why you didn't mention it in the OP.

[AoiHana]

The problem wasn't with the computer, since I tried installing two times with debian, same thing, while with Mint it went ok. I guess debian installer wasn't good, or somethin', though the integrity check showed nothing.
God knows what it was, but another distribution got the better end...

[Head_on_a_Stick]

another distribution got the better end

That's a matter of opinion