Welcome to the forum @tms
If on 2.0.8.1 or newer, maybe third-party tool duplicati-client.
If on 2.1 and willing to run Canary test build or a future Beta:
ServerUtil - How to show running backups
There is also an indirect way that might work. The job database is open during backup.
Sysinternals Handle (or similar) could likely report that to you.
I don’t think this should cause a problem, but I haven’t tried it recently.