There's no way to donate directly to Firefox development.
There is. It is called "restricted funds":
https://www.501c3.org/kb/what-are-restricted-funds/
The more people use restricted funds designation, the less bloated non-profits with wishy-washy missions there would be and the less money there would be to pilfer by the parasite class that lives in the executive roles of the non-profits.
If so, there's a lot of people who would like to do this, I believe.
Write "Restricted funds - see attachment" on a check. On the attachment list check details and a restriction such as "Direct expenses for <blahblahblah> only." If you just do not want it to go to G&A fluff fund the execs use to live a large life, just exclude G&A: "<blah blah blah> purposes only. No G&A"
Regulations for non-profits aren't a joke. If they took your restricted funds, you bet they are going to follow the restrictions.
Non-profits may hate it but at the end it is money. So they take it. If they decline to cash the check, no skin off your back.
Source: lived in a non-profit land as a tech consultant. Heard constant bitching about big donors being smart and always restricting funds above a few hundred dollars. Execs of every non-profit that pretends it cannot deal with restrictions are taking the donor for suckers and are fleecing them.
If MoFo made Firefox, this would make sense. But they don’t.
It is their problem, not my. They want money. It is restricted. Money is fungible. If they figure out how to use the money that is restricted then they need to spend less unrestricted money.
Thanks for elaborating though! I didn't know about this feature of donations.
Here's a related discussion on exactly this topic, from 11 months ago. I see that it was you who mentioned restricted funds in that thread, too. https://news.ycombinator.com/item?id=20874641