I never tried Signal or Whatsapp, but I'm on free and federated #Jabber/#XMPP since 2014. I came late to the party — Jabber exists since 1999. At some point, Google chat federated with Jabber, but they stopped it, because #BigTech does bigtech things.
Bridges from Jabber to Whatsapp and Signal do exist, i.e. #slidge, but because WA and Signal are anti-federation, the bridge can only work, if one has an account on WA/Signal 😞
Anyway, all friends and family are on Jabber now.