I think the problem is just that some are not (cf. April Release macOS requirements represents significant change). If the users of these are still happy with their performance (as in the linked thread), they will be unhappy for being cut off.
On the other hand, this will always happen - at some point around 2031, M1/M2 won’t get updates anymore, and they may well be just fine as Roon Servers otherwise. On the other hand, I’m not sure any user of commercial OSes should be very surprised by this, and it’s even more predictable with Macs. Maybe the longevity of Macs is a curse in this regard. (And Roon OS is a blessing)
Is running the official Roon Server Docker image for Linux in Docker Desktop on the Mac going to be an option? Will it be supported?