I'm curious what the breakdown of donations is. I only have 1 contact with a $10/month and 1 with a $5/month badge. Of course there could be others not displaying the badge. Signal really needs 500,000 people giving $20/month and plus the rich guys giving some millions on top of that to be in a safe financial position.
Maybe something that could be done to encourage donations is have the client estimate how much raw infra costs your usage created and display in the donation screen.
They actual costs are apparently about 1 USD per year per user. I usually at least double (usually more) my incurred cost when the donation is optional, to cover for those who can't or won't pay, but paying 240× the cost price seems wasteful as well when there are other nonprofits that can do more good with every dollar you give them (be it solving poverty, climate change, whatever you find valuable) rather than one which has mostly fixed fees
I'm donating more than my costs deliberately because I fully understand that most users are not going to contribute money, full stop. I need those users though, because they are the people I want to privately communicate with. So the obvious thing to do is pay for as many other users as I can. If there's 50M monthly active users, and if 1% of them are like me and highly value Signal, then each of us 1% users can pay $20/month and cover the entire operation. Then the contributions of the super rich donors can be saved to rebuild the war chest.
$20/month is nothing to me considering the value I get. I understand that most won't feel that way, which is why I'm only appealing to those who do feel as I do to just get that recurring donation going now.