I don't specifically distrust the code. I dont know where my data on that hosted service ends up since its rather private information. So self hosting is an option if i can see a demo without providing my personal data.
> but I'd also skip using their hosted service given that Traccar is a Russian company.
Why?
I mean... I don't live in russia, russian police/fsb has no power here, same probably is true for you too, and if i/yo do something stupid, the chances of a russian company giving data to my/your local police is much lower than if I/you used some local company. Why should hosting in russia be problematic here?
How else do you expect to test something? You either install it on your own server, and send your private data to your private server, or you use a public server and give them data.... what third option do you expect?