There aren't many switches supported by openwrt, and even less with PoE.
Those which are, are mostly RTL838x based.
Here's a list:
Those devices aren't very fast, when it comes to routing, I'd probably get a proper router, instead
of using one of the ports for WAN.
Check Support for RTL838x based managed switches and https://svanheule.net/switches/ , there might be more switches coming.