When I started I looked for generic I/O boards with Ethernet, a processor I could flash (Atmega), opto-isolated inputs and generic outputs. Didn’t find anything. Ended up making my own.
Two versions so far:
Trying to gauge interest on the 2nd version to determine whether it is worth producing for sale.
Few people seem to care much about Ethernet though, most just use WiFi (and experience the associated problems )
)