technically you're probably less secure with a mainline kernel Linux phone vs GrapheneOS. Privacy and security should be comparable to desktop Linux tho since that is what your running, just with a mobile friendly DE. I used a #pinephone running #mobian (Mobile Debian) for about 2 years but the hardware was painfully slow. Currently use a Pixel 8 with GrapheneOS for my main line and a Poco X3 NFC running #postmarketos for my secondary. Most programs/apps I use under #gnome on desktop adapt and work perfectly fine under #phosh on mobile. If you have a supported device and can deal with not having banking apps and (usually) a camera then mobile Linux is worth taking a look at. Almost every service I use has an app that adapts to mobile just fine. Just keep in mind what you're using. I'd guess it's only a matter of time until until some security/privacy oriented distros become available.
GrapheneOS (npub1kwa…e0nj)