Hello

I have a Ryzen 5 1600 CPU that I don't use anymore

I was thinking to upgrade my very old Athlon XII 250 that I use on my Vanilla server (works just fine though)
is there any specific AM4 motherboard I should look for, or at least a specific chipset I should avoid?

Thanks

Having run Ryzen CPUs since I preordered a 1st gen, I would recommend any B350 or B450 motherboard for your 1600. The B series is the mid-grade chipset - I would avoid the budget A and the deluxe X series, as the former are always a bit questionable and the later overkill, especially for a build with a very old CPU.

The B450 will be cheaper to buy new right now, where the B350 used could be much cheaper (free, if you know someone who upgraded and is generous).

Be careful with the latest B550. It supports features (such as Gen4 NVMe drives) which your CPU doesn't support, but in the process some motherboards have BIOS which have dropped support for older generation CPUs. You need to check the manufacturer's documentation or you may find yourself chasing issues.