APK won't install on Android 11 with error 'You can't install this App on your device'

Hello!
Quite annoying error I got: ‘You can’t install this App on your device’. Unfortunately I can’t give any further infos on this error since nothing more is displayed. More surprising is the fact that it once was installed on the device but something must have changed… either by me or something else.
I tried messing with some player settings like where the file should be installed or required internet connection but nothing helped so far.
Thanks for any hint!

Edit: Unity is version 2018.4.23f1

Could you please attach Editor.log after the installation fails, as it may contain additional info?

Sure, thank you. Since I am unexpierienced with troubleshooting Android I think you want me to add the Editor.log from Unity after I built the file and Unity tried to install it on my mobile phone?
Here it is (since I am not allowed to upload .log files i zipped it).
When I try to put it directly on my mobile phone i get the error in the console:

But the SDK is set preferences:

and also the adb is present in the given directory
6556306--742507--upload_2020-11-24_16-3-19.png

6556306–742498–Editor - Copy.zip (111 KB)

And now I finally found the issue when posting the reply: It says when directly installing it to the mobile phone: INSTALL_FAILED_VERSION_DOWNGRADE
So uninstalling the application and increasing the version inside the playersettings helped.
… is there a way to reset the version count? I guess not, right?

You could also uninstall app from phone manually.