Current recommendation (EU) for radiator thermostats working 100% local (without cloud)

Hey fellow experts!

We get quite a few radiators replaced and I want to to directly use smart thermostats on them. I started experimenting 8 years ago with Max! bei ELV, which is quite cloud-oriented, though. Quite the same is true for HomematicIP, Nest and so on.

As I am very happy with the smart sockets by shelly and others with Tasmota and light solutions with Zigbee, I only want a system which can run a 100% local. It would be okay if it was cloud-capable, but would accept cutting the connection by the router/firewall.

Any recommendations? Thanks a lot!