I used a Pinephone Pro as a daily carry. It wasn't actually the lack of apps that killed it for me. Fractal, the Gnome Matrix client, was great. Phone calls were functional, Mobile Thunderbird (thanks to PmOS packagers), Mobile Firefox, and Gapless (my preferred music player for mobile) all worked well, and I could actually use native apps for most of my use-cases, like Gnome Password Safe (the Keepass client), Gnome Calendar, etc.
The battery life and performance absolutely murdered it though, and it was worse for the Librem 5. The PPP at least had external chargers for sale, and was made to be compatible with Samsung batteries, so I could, and did, carry 3 on me. The (larger) dev community for the PPP also put out things like Sleepwalk (to periodically wake the modem for notifications), and had more stable, cooler- and longer-running modem software for the PPP.
Somehow, the software for Linux Mobile isn't impossibly far off. Modems are a bitch though. Like, buy Qualcomm stock levels of "This shit is insane, how does any of it work as well as it does".