Get something mainstream. As long as the bike has one of the following engine systems: Shimano, Bosch, Specialized, Mahle, TQ and a couple others I can't think of off hand. Any of the other weird ones are often impossible to diagnose and work on
Bafang motors are a crap shoot. They make a couple that are okay, but also a lot of low end, sketchy systems.
Electra has a couple of cheaper models that come in under $2k. While the motors themselves aren't unsafe, I think the bikes themselves have underpowered brakes and the like. Something like the Specialized Globe is $2800 and is a pretty solid, utilitarian platform.
Avoid Rad Power, Lectric, Super 73, and any of the other weird, fly by night direct to consumer Asian brands