To answer your question about Android apps, there is an application called Waydroid that can run on Linux phones. This essentially emulates Android and you can install apps on there. Some Play Store apps require access to Google Play Services, and even though MicroG tries to emulate it without being as privacy invasive, it is not perfect and some apps won’t run well or even at all.
I only use it for a few things that do not have any way to access through a web browser.
I daily drive a Librem 5. First thing to note is do not expect a well polished experience. Battery life is bad, only about 4 hours of light use, and 8 or so hours if left in suspend. It can do VoLTE, send SMS, use web apps and any apps coded with libadwaita or kirigami. Other desktop apps can be forced to scale on the display, but it won’t be perfect.
I use Signal desktop as my main means of communication on the Librem 5. I have a spare normie phone for setup, but Waydroid is an option. I do use Waydroid for a few apps that have no web browser equivalent.
Idk, all I can say is, you have to really want it to live with it. I don’t do gaming or heavy social media use or anything removed that, so it is just fine for me. But it’s definitely not for everyone.