Net Monitor is incompatible with Android 10+ and should be moved to the archive
Net Monitor doesn't work on Android 10 and newer anymore. To increase privacy Android 10 restricts access to /proc/net which Net Monitor relies on to log network access. The app would have to be completely redesigned to work using the Android VPN API.
This is also confirmed here: https://github.com/SecUSo/privacy-friendly-netmonitor/issues/74
As you can see in the Google Play Store reviews, users are frustrated with this fact and the app has gotten a lot of bad reviews lately: https://play.google.com/store/apps/details?id=org.secuso.privacyfriendlynetmonitorapp&hl=de&showAllReviews=true
As there are no signs of a fix for this issue and Android 10 is now out for over a year, the app should be moved to the archive and a statement like this could be added to the description:
"This app is incompatible with Android 10 and newer. As an alternative you can use NetGuard Pro (donation version) to log outgoing traffic"