Short answer: any B550 that was manufactured after the release of Ryzen 5000 CPU's.
Ryzen 5000 was released over a year ago so you're highly likely to get one. The only problem is something called 'new/old stock'; old stock that retailers unload at low prices during discount season. Any board, from any mfr could be 'new/old stock' for any given retailer so ask your seller..
If you're really worried just look for a board with a BIOS flashback feature. MSI has several such boards...so does Asus. With that feature you can flash update a BIOS even without a CPU.
Suggested: Asus B550(m) TUF Gaming Plus, MSI B550m Mortar, MSI B550 Gaming Plus all have flashback.