@sportsmen Yes. That extension has "manifest_version": 3, in its manifest.json file. The reason I asked is that there are/were some Chromium issues with inactive server workers. Something about service workers can't be persistent anymore in V3. The extension has to save state and start the service worker back up when needed and load the state back in. I guess some extension authors haven't figured that out yet.
Are you using Opera GX or regular Opera? The worker goes inactive for me in both. I also tested in Chrome and it goes inactive after a bit too. So, it might just be a bug with the extension.
As for the behavior of the extension itself, I don't know how to use it to test that.