I am really fed up with WhatsApp (closed source, jurisdiction that may impose backdoors soon)

I would even try to convince friends and family to move to something else but to what?

Signal so far has been the obvious choice but the fear that they may impose backdoors becomes more and more concrete.

Threema seems great! But they want 3€ and there is no chance in hell that my friends and family would pay it.

I saw a bunch of options on https://european-alternatives.eu/category/instant-messaging-apps but I would like to gather experiences and opinions