If I had made a post for each problem, besides cluttering the forum, it would have been impractical. The problems are related to each other because, in the end, what really mattered was having a correct and well-done graphics card transition.
I really like using Manjaro; the team’s work is amazing. I use the forum for helping me (when needed) and read the documentation about updates. Everyone has their own life, and I don’t want to bother anyone. So maybe less sarcasm is a good way of dealing with people who don’t know as much as you do.
So, as promised, here is a step-by-step of what I did.
- Since I was using Nvidia and my updates was delayed, first of all, I changed to open drivers (Nouveau) and the removed the Nvidia drivers.
- Update the system and reboot
- Moved to UEFI (there is a good tutorial in Manjaro Wiki, I used chroot trough a live USB). In my case, my disk was on MBR, had to move to GPT (this procedure has a risk of losing data).
- Replaced the old GPU with the new one, and everything worked just fine, since the AMD drivers work out of the box.
Thanks everyone for the help and patience.