if the app is in reasonable use (eg. for some weeks, with some amount of messages and chats created), we want to add a device message that ask for donations.

the text of the device message could be eg.

❤️ Seems you're using Delta Chat!

Please consider donating to help that Delta Chat stays free for everyone.

While Delta Chat is free to use and open source, development costs money.
Help keeping us to keep Delta Chat independent and make it even more awesome.

https://delta.chat/donate

once this is merged, we consider to add later similar messages for "ask for review" and "please set an avatar"