Control Relayboard over ethernet (Wired)

Hi all!
Big homeyfan, got the Pro (2023) coming up soon - which introduces a problem for my current setup.

I control some stuff for my swimmingpool with homey. I’m doing this with an 8-relay-board, controlled by an Arduino, which is controlled with the long-time abandoned HomeyDuino - which will not be supported by Pro (2023). The app itself is already ‘limp’ (several functions not working anymore, yet with some creativity you can work around it).

The pool is in the garden, and the pool-tech-room is a below-ground sort of bunker accessible through a hatch in the garden (4 meters long, 1.20m wide, 1.20m high or so). No wifi there. The devices to control mostly use low-voltage signaling.
-Poolcover: hijacked the controlbutton, by connecting the correct wires with a relay for either opening or closing the cover
-Poollight: On/Off (220v needs to be switched), but also: Off-On QUICKLY to change color (it loops through several color if switched off-on within a second)
-Poolpump: Digital switching: relay 1 = on, relay 2 = low speed, relay 3 = mid speed, relay 4 = high speed, relay 5 = off

Does anybody have a nice suggestion as to how control this reliably, without HomeyDuino?
I have some thoughts, but am wondering if I’m missing some obvious easy way…

(currently the plan is to rewrite the code for my Arduino to present itself as a webserver and react to requests over HTTP)

-Relay 1-5: Poolpump, digital signaling with low voltage
-Relay 6-7: Poolcover, digital signaling with low voltage
-Relay 8: Poollight, 220v switching but has to be able to reliably switch several times fast (twice <1 sec)

Use Webhooks?

May be Tasmota.

And Homeyduino will be updated: