Which open-source operating system(s) installed to all mobile devices (laptop, tablet, phone) would work nicely together like Apple devices do?

To improve Android-application function on the go, AOSP-derivatives (LineageOS, GrapheneOS, /e/OS, CalyxOS, etc.) are also tolerated, at least on the phone. This because so many people say mobile Linux (PostmarketOS, Sailfish OS, etc.) is not so nice yet in daily phone use.

This question didn't come from me originally, but I'll add my context anyway:I come from Ubuntu (eww, Canonical) and Android (eww, Google, nope!).

I currently have Linux Mint with Cinnamon desktop on the laptop, and because of the bugs, I've been considering moving to something else with KDE (serious desktop UI), maybe OpenSUSE because its roots are so European.

I tried Fedora with Gnome on a tablet I had 2025, which seemed fine on a touchscreen, unlike Fedora with KDE.

My phone runs /e/OS with the default Nextcloud hosted by Murena (the company behind /e/OS), which is fine, and I appreciate that /e/OS can be bought pre-installed, and that it supports bootloader re-locking (against pickpockets) on many devices (Fairphone and Shiftphone of the European ones).

Special thanks to Firefox for a unified experience through a Mozilla-account. More of this kind of unification would be welcome.