Hi,
It rather depends on your knowledge of microelectronics - if in doubt, please stop and don’t injure yourself or someone else. Mains voltages are rather dangerous, and large electrolytic capacitors (like those on the PSU section of this board) can hold a 400V charge for hours (good kit uses bleed resistors to discharge, but not all kit is good…).
I can see:
- dedicated driver chip in the middle
- Power section on the right with common mode filters, and two relays
- Top left has an interesting board slot - just the sort of slot a Tyua or similar control board would solder into.
There’s three main approaches:
- Find a similar device, or upgrade module to replace the control gear (you’ve already found the common AC fan control modules)
- Work out what the motors use, and replace the lot with a custom board (e.g. trace out the relays and power control section, and replicate using an ESP). Flipped digital camera photos make PCB reverse engineering easier.
- Reverse engineer the possible missing control board connections, and possible interface to the uP top-right. Logic analyser and isolated oscilloscope probe not included!
If this helps, 
this post!