Specifically, do debug calls get logged if a command never terminates? For example, what happens if a debug call occurs before a non-terminating transaction in the command submission?
Depends on where you look:
In a real ledger, they should get logged as they’re executed so even for a non-terminating transaction you will see them.
In Daml Studio they only get logged at the end so you don’t see them if your transaction never finishes.