How can a google or Microsoft account be used for syncing license across platforms? Can you explain with more detail? Is there any other app that does it? All solutions I can think of require some backend/server on my end.
Also, when one purchase would work for all platforms, I would have to price the app significantly higher (at least twice as high) in order for me to have a sustainable business and be able to keep working on the app. Would you welcome such change? It's not about the money for you, just the "weirdness" of paying multiple times, if I understand correctly?
The only alternative to a platform-bound one time fee is a subscription (just how basically any other app is doing it nowadays). How much would you be willing to pay for such a subscription?
What other Cross-Platform app has a better system in place? I am happy to look at how they are doing it and how much they charge. So far, I didn't find any other app that works cross platform with a shared license at a lower price than WorkingHours.