Actually after EVERY reboot or PTP of Homey all Tasmota devices are marked as unreachable. After a restart of the Tasmota App every device is reachable and works again.
A reason could be that the Tasmota app restarts before the MQTT client app finished its restart after a Homey reboot.
The problem is, that I could forget to restart the Tasmota app after a Homey restart and a lot of tasmota devices will not work. Another problem is that a automatically restart will not work correctly.
Homey 5.0.2
MQTT Client 2.3.0
Tasmota app 0.8.5