If you are feeling playful - I am experimenting with a "lobby" group concept on Signal, taking advantage of the group link feature to avoid posting my phone number on the web. Once there - you can DM me and leave the group.
Sure, a spammer can simply join, harvest my number and leave, but it adds an extra bit of work that most of the current bots probably aren't ready for. No idea how effective this will be, but it seems fun to try.
Ultimately, I think the solution to spam is something based on OAuth-like authorization tokens issued to senders, which can then be revoked in case of abuse - but we aren't there yet.
Around the web you can find me at: