If you are willing to use Signal, you already don’t mind a tiny userbase, so why not use Session (or maybe Matrix) and enjoy privacy, security, AND anonymity?
Signal has always been clear that privacy!=anonymity and regards people who want both as both stupid and unusual. Its always been a weird dance to watch.
I haven’t done any Signal app recruiting in my circle of contacts (in fact, I don’t think I’ve talked to anyone about it) and I have 14 contacts that have it installed at the very least. I don’t think it would be a huge push to make Signal more prevalent.
The uphill battle is making a dent in iMessage adoption, which seems to be deeper and deeper entrenched every day.
They dropped the native sms integration. IMO, that was the best tool for adoption. Make it seamless for people to move over from their native SMS messenger and people will use it. Going full closed, only signal to signal, meant I needed to use multiple messaging apps for different people. And I had to remember who is on which. It’s been a headache.