On my laptop with hybrid Intel and Radeon graphics, upgrade to mesa 20.0.7-1 made the system unable to boot.
Previous version mesa 20.0.6-2 boots OK.
One way to workaround an unbootable system is to use TTY while trying to boot:
- press Ctrl-Alt-F2
- login normally using the TTY terminal
sudo pacman -S --needed downgrade downgrade mesa # select previous version 20.0.6-2
You may need to downgrade also mesa-vdpau, but unfortunately I couldn’t test that here.
Note: if your system boots normally with the latest mesa, then you need to do nothing.