This would however also mean giving up on the core principles of free/opensource software and turning it into shareware(?). Why would I want to contribute to that software?

I think the patreon-like idea is great! Similarly to how netflix turned lots of people that previously watched movies for gratis on streaming sites into paying customers, making paying money for software easy and convenient should have a large impact.

The big question are who should handle the financials of this and how the money is then divided.