How can you test for bad RAM in a MacBook Pro 2019?

Just use the default MemTest86 settings since modifying any MemTest86 settings will cause the tests to fail or break on this model laptop. I forget what exactly occurs, but I know only the default settings are acceptable on the T2 Macs. The free version only allows you to perform four loops instead of unlimited.

Your profile is showing a 16" model. It would not be surprising for the Logic Board on that laptop to be bad since that model has an extremely high rate of failure.

Has your laptop been experiencing Kernel Panics? If so, then unless you are using some junk apps which could cause problems, then it is most likely a hardware issue with the Logic Board. Especially if you are seeing any "ProxiedDevice-Bridge" panics or "GPU Restarts". Junk apps are anti-virus apps, cleaning/optimizer apps, and third party security software since none of them are needed on a Mac and they usually cause more problems than they solve because they interfere with the normal operation of macOS at a very low level (aka causing system crashes & performance issues).

intel Mac?

you can create a self-booting memtest86 USB stick, which can access all of RAM memory and run for days.

<< I also have Avast installed, so I'm wondering if I should remove it. >.

YES, and you should never install it again on anything, ever.

Effective defenses against malware and ot… - Apple Community

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