Problems with kept back packages

[shadowmaker]

I have no idea how to solve this problem: I installed a Debian 10 in my 
computer. The GPU was only supported with linux 5.8 so I updated to 
bullseye. I don't know how to configure correctly the sources.list file 
so I just changed all the 'buster' for 'bullseye' and it upgraded well 
(but the Debian-security failed I don't know why. It would be 
interesting if someone helps me with that). I rebooted to use the last 
kernel an the GPU controllers worked this time. But, the serverx (I 
installed GNOME) didn't work. I tried to upgrade and... More than 500 
packages were kept back... I am using bullseye so I don't think I have a 
deprecated version. But  don't know how to configure the sources... 
Could someone send me a configuration for the last bullseye system?
Thanks in advance.
Happy hacking!