Are there any (ideally waterproof) compact devices with long battery life (months~years)?
I've mostly built my own, but I did order a SeeedStudio T1000-A a few weeks ago, and it's arriving next week.
It's IP65 rated and estimated 4 months battery (with 1 hour updates). It also has WiFi that you can use with Google's geolocation API when GPS is unavailable.
However like all LoRaWAN stuff, you do need coverage of a LoRaWAN provider. I use The Things Network since it partners with my city, but Helium is another option (although not currently supported by Traccar).
On the website I only found a long list of supported devices with brand name search and protocol type.
Traccar just supports The Things Network webhook API, in the TTN Mapper format (another tracking service, although public). Anything supported by TTN Mapper should work with Traccar.