Where is the "Don't switch" option? Because as much as I hate that Facebook bought them, they're part of what I would call "critical social infrastructure." Asking to leave WhatsApp is like cancelling your contract with your ISP and going offline just because you don't like the company.
If I choose to stop using my ISP, I have no need to "go offline". I can simply switch ISPs and I still get the exact same internet. This is why we must not fall for this "critical social infrastructure" trap. No one company deserves our business. We can and should go elsewhere.
Messaging should be like the internet. If I don't like my messaging provider, I should be able to switch and still message everybody. Ideally, I would be able to bring my identifier with me. Luckily, SMS already provides this. I therefore recommend old-fashioned SMS/MMS for messaging. If you want something more "modern", I would recommend Matrix, as it is the only "modern" messaging system that wants to allow people to switch providers while still messaging the same people.