without including any battery or need of extra wire I have been able to replace my wifi thermostat.
I have pulled down my thermostat and I have replaced with ZBMINI-L2 ZigBee (the one with just line wire) + a virtual thermostat (GitHub - jmcollin78/versatile_thermostat: A full featured Thermostat for Home Assistant: presets, window, motion, presence and overpowering management) this is the best and smart way to manage a thermostat without spend too much time on integrate wifi stuff, of course my solution is not opentherm but to it is enough.
I’ll upload some picture later on.
