It is a standard Chinese sensor (256x192) dongle camera, branded up for Topdon with some design and price point choices made.
Topdon are primarily a supplier of car mantenance equipment.
No battery is probably a good thing.
You are right to consider if dongle-attach is right for you. It mainly comes to breakage risk and whether you'd get your phone into those situations. Clearly there are build cost savings as a fulll camera needs processing and display, which is being provided by the phone.
Fixed focus has been an issue as some brands are not actually focussing the cameras at build, just screw the lens in and hope.
Assume you have found:
https://www.mbreviews.com/topdon-tc001-thermal-camera-review/I do wonder how well 'auto' mode would work, you would not want to be fiddling about with range / span settings while rummaging about in a loft looking for bees.
For that money one other option would be a decent condition ex fire-service camera - which were built like a tank of course. They are fully automatic and usually 320x240.
Bill