I don't know. Termius doesn't do that does it? (Background App Refresh I mean)
The workaround Termius apparently uses is absurd (and rather amusing): it adds location tracking it doesn't really need. Because apps that have location tracking enabled don't lose their connections:
https://support.termius.com/hc/en-us/articles/900006226306-I...
This is a clever solution but it does have a Kafkaesque quality.