Lol it’s a global warning.
F-Droid is a trusted source.
Just be careful for some apps of F-Droid (check always the permissions, the anti features…)
I contacted the author of the application and he’s ok to update his app. But he has no idea of what to change on his app to make it compatible with recent android. Does anyone has an idea about that?
The Privileged Extension doesn’t work with a device that isn’t rooted (have a look at its description). Uninstall it. Then F-Droid app should work. Apps are installed via system’s apk installer so every install/update must be confirmed manually.
According to that a warning is shown for apps built for Lollipop or earlier… so to avoid it the app needs to target sdk >21.
Also, its just a generic warning that doesn’t indicate anything about the quality of the software (other than it targets older devices). It doesn’t necessarily need to be fixed (so in the worst case just ignore it).
The second notification comes from the system not from F-Droid. How did you install the outdated app? As the client doesn’t work for you, I suppose you downloaded the apk from the website and installed it directly from the download folder. The system installer noticed that this app wasn’t built for your Pie device but for older Android versions, might be eventually inappropriate and prompted the message. (This is part of Android at least since Android 6, Marshmallow, and not a brand new Android Q feature).
The first mentioned notification however comes from F-Droid. As your device isn’t rooted the extension can’t be used and no apps regardless how old can obviously be installed.
The much more interesting questions to the devs of the client are:
Why doesn’t the error message tell us the relevant things instead of some obscure description? “You installed the extension without root access. That won’t work.”
Why doesn’t the client fall back to an installation mode without privileges when it is obviously capable to recognize the missing permissions.
Yes they are unrelated - apologies for distracting from the issue relevant to F-Droid.
Tell the author to increase the android:targetSdkVersion="21" to at least 23 in his AndroidManifest.xml, and perhaps consider replacing the existing ant build with gradle.