Here is the download page for your laptop. The latest drivers or BIOS are from 2019.
X555QG - Support
This does NOT mean that it won't work on 20H2. If there WAS a problem with 20H2 that a new BIOS or driver could have fixed, ASUS would have provided them by now.
In the first post you said...
"The laptop that I use for my field work is somewhat old, but functional, but at the beginning of January I formatted it and installed the new version of windows 10, 20H2"
My question is... why didn't you do an
In-Place Upgrade instead of formatting and doing a clean install?
You still have that option it seems.
In post #14 you said...
An In-Place Upgrade will... upgrade you to 20H2, and fix Windows... but will leave all your programs, drivers, files... untouched.
My guess is that when you formatted and reinstalled, you missed a driver somehow, and that is what made your laptop... "not work the way it used to".
Repair Install Windows 10 with an In-place Upgrade
/edit
After a clean install of Windows on a laptop... IF there are problems...it's a driver issue (or some manufacturer software), 90% of the time.
The In-Place Upgrade avoids that, by leaving the drivers... untouched.
/edit2
Back in July 2020, my brand new computer wouldn't update from v1909 to v2004. For some reason Microsoft thought it was "incompatible" with v2004.
Well, it wasn't incompatible. I did an In-Place Upgrade, and I'm now on 21H1 (one past 20H2), and haven't had any problems. I have an ASUS motherboard, btw.