using Testing, i just bumped into this bug:

https://bugs.debian.org/cgi-bin/bugrepo … ug=1030981

Where nvidia-driver can't be upgraded from 520 to 525 because there is no firmware-nvidia-gsp 525 version.

The recommended solution is to add "non-free-firmware" to the deb line inside source.list because "the firmware-nvidia-gsp package is moved from non-free to non-free-firmware".
This is the first time i hear of "non-free-firmware". But after adding it and updating repository, the only availabe "firmware-nvidia-gsp" version is still 520.56 on Devuan.