I know that older R10s with 3000 series CPUs don't support 5000 series, but what about the opposite?

I know that older R10s with 3000 series CPUs don't support 5000 series, but do the newer R10 MoBo's that came with 5000 series support the older 3000 CPU's?

I pulled my Ryzen 5900 and 3080, and other usable parts from my R10 to a better case with more airflow. Could I pop an older Ryzen 3600 into my NEWER R10 and make a "lesser build" for my 10 year old son? I still have the R10 with MoBo, the Dell HyperX 3200 RAM, a smaller 1660 Super GPU.... etc.