If I look at the HA log, the thermostat seems to disconnect and reconnect itself every few minutes. Does yours do that? After looking closer at it, I think this is an issue with the Rheem thermostat not staying connected to the home WiFi network.

Also, have you considered wiring in to the thermostat directly to avoid having to use a Rheem account?

Someone on Reddit theorized that he saw the term Delta and associated it with Delta Faucets the company, and that is where the faucet idea of his comes from.