Welcome to Manjaro!
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Please read this:
How to provide good information
and post some more information so we can see what’s really going on. Now we know the symptom of the disease, but we need some more probing to know where the origin lies… -
An
inxi --admin --verbosity=7 --filter --no-host --width
would be the minimum required information… (Personally Identifiable Information like serial numbers and MAC addresses will be filtered out by the above command) -
A weird screenshot would be beneficial, as what you call “weird”, I call “normal” and what I call “weird”, you call “craaazyyyy!”
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From your description it smells like your AMD graphics driver is crashing (and restarting itself) when coming from sleep mode.
As you mentioned 5.9 and 5.11: these are experimental kernels, and you should add both 5.4 LTS (Long Term Support) and 5.10 LTS and try those out before you do anything else!
P.S. If you enter a bit more details in your profile, we can also see which Desktop Environment you’re using, which CPU/GPU or Kernel, … you have without typing it every time