Turning on WiFi in Buster is not possible [SOLVED!]

[Bulkley]

I upgraded the kernel, and then I installed the backported realtek firmware and the problem was gone! Here is the complete solution for how to upgrade the Debian Buster kernel and how to fix WiFi problem on Debian Buster if anyone needed later.

Good stuff. Now, so that others will notice, could you edit your opening post to add SOLVED! to the title?

[stevepusser]

If you still have MX on a USB drive, try starting a live session of it

OK. Thanks to all you friends trying to help me. And sorry to not being around for a couple of days and answering too late.
And thanks to @stevepusser, I wondered what is the major different between Debian Buster and other distributions that I have tried and wifi was working perfectly on them. Bingo! The Kernel!
So, thanks to this post, I upgraded the kernel, and then I installed the backported realtek firmware and the problem was gone! Here is the complete solution for how to upgrade the Debian Buster kernel and how to fix WiFi problem on Debian Buster if anyone needed later.
Thank you all again. Cheers.

Ummm--a different kernel can be only a tiny bit of the difference. Debian stable ships with an older kernel by default, so a newer kernel and firmware is very often a solution to get newer hardware working, though. MX AHS and KDE editions are based on Debian stable, but with updated kernels, etc. for those with newer hardware that want it to work right off.

[ravy]

Good stuff. Now, so that others will notice, could you edit your opening post to add SOLVED! to the title?

Sure. I didn't know that I should mark the topic with solved flag. Ill mark it right away. Thanks.