Obviously people who cannot or will not pay...simply will not...
Please pardon any duplicate thoughts...this is my first foray into these forums and I didn't spend much time looking around, prior to this post offering some hopefully useful suggestions.
Some sort of one-time popup message after the user has been running GOS for a month or some other TBD number of hours asking them how they like the OS and if they are able to provide a monetary or time based donation.
Perhaps there could be some sort of graphic with the monthly goal and the progress towards that goal. In the event that new hardware may be required there could be another graphic with the corresponding progress. These make make more sense if the people donating understood exactly where the donation was going, but it seems that there is a list already.
How about a GOS store...where one could purchase a monthly / yearly "license"? Nothing that would be enforced, but it would serve as a token / named contribution.
What about passive income like a T-Shirt type shop for GOS clothing, pens, mugs, sticker, etc?
Is there any possibility to take advantage of Amazon Smile? I use Signal, atm, but they probably don't need my contribution more than GOS.
Or perhaps some how get Amazon affiliate "fees" using a GrapheneOS link? When people look for a new phone case they can click the link and shop, I don't think you need to have an Amazon store / favorites setup, but even if you did, it could be a list of Pixel related cases, screen protectors, etc. (with a disclaimer that none are specifically endorsed)
Admittedly, it is not clear to me how difficult any of the above might be or if they are even viable possibilities.
edit: spelling / grammar