I use a dedicated Raspberry Pi (5, previously had on a 4).

I host everything else on a different server, the HA one is dedicated. Pretty nice because then it can run HAOS and basically manages everything itself.

One factor in keeping it separate was I wanted it to be resilient. I don’t want stuff to stop working if I restart my server or if the server dies for some reason. My messing around on my server is isolated from my smart home.

I also have a separate Pi (4, previously on a Pi 1B) that runs Pi-hole, on it’s own Pi for the same reason - if it stops working or even pauses for a moment, the internet stops working.