No new info about the DIY projects…
So I ended up buying this cheap chinese product on aliexpress. "pH-W18 Yieryi-Tuya Smart WiFi, PH ORP, TDS, EC SALT S "
It work perfectly under home assistant with Tuya Local integration (be careful there is also a different integration called “local tuya”).
Now we’ll see how long the probe work and how frequently it need a calibration.
As I use it for a swiming pool I will also need to adapt the 4 probes to my filtration system. For that I will use that kind of adapter and a 3D printed cable gland to adapt a 19mm cable (the probe) to the 3/4 inch thread.
I plan to print it in ASA and polish it with acetone vapor using a rice cooker (easy and cheap method).
EDIT: this is a 3/4 inch thread not 1 1/4 (corrected above)