I run blokada on my phone, which also acts as a pseudo vpn, and that does have problems with dying randomly and needing to be restarted. not sure if it's a bug in the software or a general android issue.
Some apps have a setting to disable the notification, but all that achieves is that the app doesn't stay running in the background.
More to the point, the site reminded me that you might want to verify if Blokada is exempted from ‘battery optimizations’ (works via app info —> ‘Battery’ —> ‘Battery optimization’ for me). I checked NetGuard on my phone, and sure enough I have the ‘optimization’ disabled for the app.
(Let me know if you see this comment, or I'm gonna notify you manually.)