If your 'really old' mobo are 'Legacy only', no option for EFI (UEFI), CSM, in Bios settings would be a problem.
Ryzen 5 5600x, B550 aorus pro ac, Hyper 212 black, 2 x 16gb F4-3600c16dgtzn kit, NM790 2TB, Nitro+RX6900XT, RM850, Win.10 Pro., LC27G55T..