You need to upload you app somewhere so that your can post a link for is to test it for you on Android 10, it's as simple as that really. All this talk is going absolutely nowhere, it needs testing on A10.
Either open up the locations on the play store or unload it somewhere. Actually better still, use the beta testers feature on the play store.
Using Play Console, developers can test apps with specific user groups or open tests to Google Play users to fix technical or user experience issues before making an app available on Google Play. See
support.google.com