> That's great until someone has an app I need and chooses to only make it available on a different store.

Fair point. The company I work for would 100% now require you to do that If you want to use our software, to make it easier to comply with Qt LGPLv3.

> I'm not legally trained, so I hope they've thought of this and also have rules for these 3rd party app stores.

Isn't the idea here that you do not need an app store to require external software?