Zen3 is already not supported.
You need to buy new motherboard and processor. No way around it 😖
You need to clarify exactly what you as asking. What sort of "support" are you talking about?
Both, and we have almost no way of knowing. Technically if you dig into the EULA, they'll have some term defined (generally 3-5 years after EoS), but often times updates come out for longer if a critical issue is found - or if none, you'll see no updates sooner. It all depends.I mean support in the form of bios updates, fixing (if any) lingering issues with stability, performance, controllers, etc. on the AM4 platform.
I assume AMD does this, or is it the mobo companies?