In an earlier episode I asked for Plugs with Wi-Fi and ended up with Gosund and Tasmota . Considering this to be a success, I asked the Twitters for Temperature and Humidity Sensors. Of course, this got complicated.
Christian Kahlo mentioned GY-BME280 Sensors, which can be connected to any ESP Tasmota device, and work with the “sensors”-Edition of Tasmota just fine. Worth a try. Jens Dibbern points to generic NodeMCU modules and BME Sensors again.
Wickelkranz points at the Aranet 4 , but 150 Euro is too much to play with it randomly. This would need more pre-buy research. The FAQ is not encouraging, but the Forums are helpful and point to Github .
Sascha Köhler recommends the Wemos D1 Mini Development Board and then a DIY sensor build.