This is a good discussion for me since I too have been thinking on getting a somewhat modern AMD motherboard. Things I would like is pcie (ideally v4 but can do v3) slots (4+) and memory. The latter requirement made me think on going to ebay and getting a server board as those memory cards are cheaper. Non ECC memory is pricy. CPU, well, other than numa I do not need insane power.
I do have an ASRock gaming board that is old but never let me down. I saw a MSI X470 (as a placeholder for this discussion) but even 64GB of non ECC memory is not cheap.