A lot of people are migrating to Signal. I'm wondering what Signal's monetization model is, as they certainly won't be able to maintain the level of usage forever as a free app.
Servers and infrastructure cost money. People's time costs money. You need enough donations for it. If you don't, you have to strategize to get more.
The key distinction being that loan will need to be repaid.
> The initial $50M in funding was a loan, not a donation, from Brian Acton to the new nonprofit Signal Technology Foundation. By the end of 2018, the loan had increased to $105,000,400, which is due to be repaid on February 28, 2068. The loan is unsecured and at 0% interest.[5]