Pay for an online number, there’s one time phone number websites you can use, but services are getting better at detecting if it’s a real cell number and block VoIP numbers.
It’s good to be leary to give your number to a business or service for privacy, but there’s no valid reason to obsess about individuals getting you number on a social level, you’re not important enough for other individuals to start bothering you simply because they got your number. I have a business card I give out with my personal number. However it also means you can’t use plain texting because other apps on the the other person’s device will see from your text message that this is a live number to track and spam.
Proton is trying to do too many things and can’t excel at doing one thing. It’s getting too big beyond its capabilities which means services are going to suffer at a lower quality.
If the want blanket trust from users, remove the VPN login to make it anonymous and change the VPN code to remove all anti-features and comply with native F-Droid, other RiseUpVPN is the only choice for everybody to use.