I also use them for voip #s. I have a calyx phone so thanks to micro g im getting the notifications as they come in. If you want to make it more private. You can buy google cards with cash at a store to upload to your google account. Also use private card service to create a virtual card for payments.
Im wanting my friends to try out linux, they are all windows normies. This is pretty aggressive approach. I applaud the enthusiasm, maybe there are some people who respond. Id try my own way by finding a distro that best suited to their use case. All an all, someone is doing linux spreading to the masses and at least we can call that a win.
ESIM using silent.link = a phone line that can only be used to receive messages and calls no outbound calls allowed. However you need a phone with esim support.
Physical sim on another device: great but you need a seperate hardware and have something extra to carry and charge.
Physical sim on a dual sim phone. Easier to carry however it runs the battery faster and sometimes you can forget which sim you are on if you are quickly calling or texting.
Mains sim plus VoIP line example is mysudo- use one phone, seperate your communication between your actual number and an app with VoIP. Seperate phones # via software since VoIP is all on app side. Requires you have an internet connection to work properly. Not all services are happy using VoIP and stop you from registering or changing numbers to VoIP.
Lots to think about, best of luck.