I'm looking for a service, that replicates the functionality of email aliases, but with phone numbers.
I'd imagine having one number (99999) which I then could use with suffixes like 99999-1, 99999-2, ... etc for services like WhatsApp, telegram, 2FA, etc... if such thing even exists.
Haven’t done it myself, but his might help you for further research
iptables
https://unix.stackexchange.com/questions/264589/traffic-of-specific-program-through-vpn
network interfaces
https://unix.stackexchange.com/questions/234583/routing-on-per-application-basis