before you take the jump, consider a way lighter and easier alternative - syncthing (files) and radicale (calendar, contacts). dependable, bullet-proof, super-lightweight, zero issues - everything nextcloud isn't.
I was the happiest when I finally booted nextcloud off my network, never to return.
upgrade went without a hitch (docker), only thing needed changing is the web UI password in docker-compose.yml. everything works, UI is infinitely faster, first impressions very positive.
saw your other post as well, there's so much stuff in your stack that you have to narrow your issues down to the malfunctioning item, there's no way you're gonna stumble upon someone with your exact setup.
start with existing element x apps communicating over matrix.org (use throwaway accounts if you don't trust it) and unified push using ntfy.sh. if everything works there, then you can start replacing one by one of these until you achieve full functionality or something breaks.
aside from the obvious, wayland being the default choice on all relevant distros and DEs and being continously worked on, evermore projects switching to it (WINE most recently) whilst X11 is in maintenance-mode, the main thing for me and my deployed fleet is if you're running a modern laptop, say with a 1080p or better screen, wayland is a must. primarily because of the output (UI scaling, effortless multi-monitor dock/undock) and the input (touchpad gestures, touch screens).
if your world is a desktop with a mouse and, say, XFCE, then you have very few of these things intruding on you and you don't really ~~understand the benefits~~ benefit from it.
they are switches for electron apps, as some of them default to run under X11. so for e.g. element, it should be flatpak run im.riot.Riot --enable-features=UseOzonePlatform,WebRTCPipeWireCapturer --ozone-platform=wayland.
you can check if all your apps are using wayland by running xlsclients in terminal while you got them open; an empty response means all wayland.
maybe reword the title, as this will inevitably lead to partisan turf wars in the vein of my-distro-can-beat-up-yalls-distro and such.
as to your thesis, yes, mint and ubuntu are important and needed as beginner-friendly it-just-works solutions that have things in place (like the mentioned driver manager) that are sorely needed for noobs. once they learn what's what they are free to wander farther, as there's essentially zero switching costs when moving from, say mint to fedora.
you'll find low sympathy from experienced users as they can't relate to people who are so much below their expertise level. case in point, a buncha people already mentioning package managers, ignoring the idea that a noob doesn't know what that is.
if you've installed flatpak recently, say F40 onward, it should default to user. if it's an old install then your flatpaks are system-wide. there isn't a downside for either case per se, but user being the default for the future prevents potential issues.
my issue is, when I need to edit a .desktop file (to include ozon flags and whatnot) for a system-wide flatpak app, plasma doesn't edit the app's .desktop file but incorrectly inserts a symlink to the user-wide version (which doesnt exist). there are ways around that, like removing the symlink and manually copying the file from /var/lib/flatpak/wherever to ~/.local/share/applications/ and editing it there, but then plasma doesn't pick up the change immediately so this works better for me.
no help to you, but a heads-up to anybody yet to deploy disks in such a scenario: always use encryption by way of LUKS2. you can set it up easily to unlock it on boot by a key file on the boot drive, thumb drive, TPM and such. so when a drive gets sold, RMA'd, etc., you got none of these issues.
source: sold my old drives recently and the shred procedure took ages. the new ones are encrypted so none of that shit no more.
can't help with the switch but if your monitor has multiple inputs, you can use ddcutil to switch between inputs. so for me it's:
ddcutil -g PHL setvcp 60 0x0f # DP1
ddcutil -g PHL setvcp 60 0x10 # DP2
ddcutil -g PHL setvcp 60 0x11 # HDMI1
ddcutil -g PHL setvcp 60 0x12 # HDMI2
then you can use udev rules or external triggers to switch, e.g. KDE connect's "Run Command" etc.
for uploading, absolutely use syncthing. you can set it up so that it works in only one direction, i.e. phone to server, so any file that appears on the phone's download folder gets sent to the server. the one you want is syncthing-fork on fdroid.
as to listening to the music via youtube check out innertune, also on fdroid.
As of right now, Plasma Bigscreen isn't available for public use yet.
docker?