I have decided this approach is such a pain and hassle that I have had to change forms. Mostly due to modern societies infrastructure making it truly impossible.
I moved all phone related things, programs, apps, anything but dumb flip phone calling and texting to a x86 based tablet. (Even a wwan or 5g sim capable device doesn't have a cellular modem so the easiest route is this)
Hotpot or cable tethering from sim card 5g/4Glte/volte from a smart phone, with your carrier sim of choice, best to pick a device matching their cellular band support in your part of the world. Routing calls /texts to the desktop Linux device of your choice laptop/tablet, 2in1, device of your choosing basically. Using the phone for nothing except internet period..., perhaps a backup device if ever needed worst case if your main goes down or breaks.
Secure and private as one could get, and totally power userable due to linux desktop capabilities and granular controls of literally everything, while still having the best reliable internet coverage, with traditional calling and texting for 2fa and other big corpo stuff. Yes the sim is tied to your real identity, but the actual day to day is much more private and secure than mobile, seperate device, vpn, LUKS drive, veracrypt, all desktop x86 (distro of your choice) Linux abilities. Close as one could get without living under a rock daily. Backups full and snapshots offsite sent to NAS or true cloned drives.
What do you think?
Then you harden the hardware further (so many ways to list again device dependant), and software as well (depends on your OS and needs/wants). (Qubes is too beefy to run all day as a phone replacement regardless of hardware. Batteries are the weak link) That being said pick any distro you feel good about and go.
This form is the most stable method, while being realistic to the goal. I have my own personal preferences for which devices, distros, settings, etc. That I can use daily.