Freezes after certain time when screen locked

So today I've installed an AMD RX 6600 card and ZorinOS 16.2 started normally and everything looks fine.

However, when the system has been locked for a while (pressing Ctr-L, then short show of Lock screen and monitor goes blank) the system freezes. If I press the numlock or capslock key, the led on the keyboard doesn't go on/off.

If I lock the screen, wait for couple of seconds and move the mouse/press a key the Lock screen appears and I can login normally.

I didn't have this problem with the GPU of the processor (AMD)

Also I have no idea how much time it takes for the system to get into this frozen state.

The page at Activate AMD Radeon Graphics Card - Zorin Help shows how to install the official AMD but I'm getting dependencies errors so that's not gonna work.

Similar (but more severe) symptoms here:

If you have an AMD CPU, do you have the AMD Microcode installed?
sudo apt install amd64-microcode

If you have an Intel CPU, do you have the Intel Microcode installed?
sudo apt install intel-microcode

Do you have the latest AMD drivers installed for your GPU?

Other people having similar issues have tracked it down to the CPU entering a c-state so high that it dumps the GPU off the bus... AMD appears to glitch on c-state 6, Intel appears to glitch on c-state 10, which either completely freezes the system or allows the system to remain operational but the screen is blank. You might try limiting your CPU c-state:
intel_idle.max_cstate=1

I'm unsure if that works only for Intel CPUs, or also for AMD. If that doesn't work, try 0 (which keeps your CPU from entering any sleep states). If it does work, iterate through the c-states one at a time until the behavior repeats, then back off by one.

If you have an AMD CPU, try adding this to your kernel command line:
amd_pstate=passive
That'll give fine-grained, continuous frequency ranges for the CPU, rather than the standard 3 p-states, if your BIOS, CPU and kernel are set up for it.