Mine is my first machine, ASUS P7P55D-E-Pro, which had snow leopard on it using rboot (iboot gave me problems I seem to recall), and this was in 2010 I believe. Currently sits happily on Mojave as my crushftp and Plex server, chock full of drives. Would love to update it - haven’t had the time to do the reading on opencore yet (and I should do my main machine first, that’s still on Catalina.)
I did have a GA-H61M-USB3-B3, which would still be in use had I not had a slow pipe leak on it without knowing for a couple of days. Good to see someone’s still got one ticking along.