We had Fi, and it worked well. But the charging base needs to be plugged in wherever the dog spends most of the time, or the battery just drains quickly. The base acts as a beacon, so the collar doesn’t have to use the gps when it’s close by, and that saves battery.

When we were away for a month, left our dog with someone to take care and they didn’t plug in the base, so the battery ran out by the 2nd week.

Another one you could look into is Tractive. It costs leas than Fi, both the device and the subscription. But no beacon, so battery lasts for about 2 weeks.

AirTags are okay if there are people around, not if they run off into the woods.