I would, but I don't know anything when it comes to programming.
The only thing I know is that I want my N900 to become my main device again and I want to get rid of an Android device.

Hmmm..I think that Gadgetbridge is an open software. I will link its page on the github here.. https://github.com/Freeyourgadget/Gadgetbridge

It would be amazing if someone could port this app (I can test it, at lest for Mi band 2) on the N900.