iOS companion app high battery drain in background

I run my Home Assistant on my Synology NAS as ISO image. Couple of months ago, I noticed that battery life on my iPhone is dramatically decreased. I started digging and step by step disabling everything in sensors section, even switching off “Background App Refresh” and “Focus” reading. Nothing helps. Why the app is running in the background even if I told it not to? How to fix that? Delete and not use?
Please help.

Is there any update for this question?