IKEAs Trådfri plug can be adopted into anything that supports Zigbee. Works out of the box with Zigbee2MQTT. No flashing required.
wigit
No doubt an unpopular opinion, but I'd rather keep the IP rating than be able to swap my own battery without the phone becoming a literal brick.
I doubt this is a scenario where we can have both.
You should check if you can put your BT router in bridge mode.
This is typically how we used to configure these kinds of setups. This should allow the router you place incide the BT router to get your "outside" IP.
I don't know if BT has any limitations on this, though, but it has worked with all ISP's where I am located.
https://gizmodo.com/google-removes-nearly-all-mentions-of-dont-be-evil-from-1826153393
It's been a while since they distanced themselves from that motto.
But you can still buy all the older systems. It's not like they stopped producing or supporting older standards. Both my local shop and the webshop I use have all cassettes from 7-12 gears. Neither currently has 13 gear cassetes, though.
In my last two phones I have used eSIM, but I still have 6 of these in a neat row on a magnet above my desk.