(2023/05/07 EDIT): I stumbled back on this thread while revalidating some thermostat specs. I’m currently midway through my bathroom remodeling with Schluter Ditra Heat materials and I ended up getting the Sinope TH1300ZB instead of the Schluter thermostats. I hooked it up to a 240V source when I received it and it was easily picked up by ZHA. It seems some guy made some important contributions to HA for Sinope Zigbee devices!
FWIW : https://community.home-assistant.io/t/compatible-electric-underfloor-heating-thermostat/114791/15
I saw some successful HA integrations claims in the Amazon reviews of that thermostat as well.
I’m also looking to install radiant floor heating soon so I’m thinking of trying that Sinopé thermostat solution.