On another thread, someone said the crashes completely stopped once they swapped out the motherboard. Not suggesting you do the same but it might be a good idea to play around with the BIOS settings in case there's something in there causing it. For example, I'd get random reboots both in and out of games until I found an option to let the motherboard control the PBO parameters instead of following the official AMD spec.
Right now I've been running FF14 pretty much all day, every day for a couple of weeks on a 5900X/3080 Ti and no issues at all. I do need to use a different OC profile for the GPU though, the higher one I normally use FF14 doesn't like it and crashes the nvidia drivers every so often. Also if it helps, my motherboard is a Strix X570-E.
Basically don't rule out the motherboard and/or BIOS settings being the cause.