Cannot run Flatpak nor Snap applications

Hello everyone,

After using Manjaro with xfce for a few months I installed Manjaro with KDE Plasma on another machine (both installations through Architect). I am unable to integrate Flatpak into the Plasma machine.
I can install packages through Pamac without problem, installing through CLI gives a warning that:
/var/lib/flatpak/exports/share
/home/p/.local/share/flatpak/exports/share
are not in XDG_DATA_DIRS.
After installation I can run application neither through Pamac, nor can it be found in my programs. It can be run through CLI by using:
flatpak run 'name'
So I thought that setting XDG_DATA_DIRS correctly should solve the problem. First I checked the value of this variable:
echo $XDG_DATA_DIRS
and it produces a single empty line. Arch wiki (1) states that it should default to /usr/local/share:/usr/share.
Also setting XDG_DATA_DIRS to /var/lib/flatpak/exports/share:/home/p/.local/share/flatpak/exports/share or /var/lib/flatpak/exports/share/:/home/p/.local/share/flatpak/exports/share/ through:
export XDG_DATA_DIRS='one of the above strings here'
ensures no warning before installation. Rebooting resets XDG_DATA_DIRS to nothing but apps are still not to be found.

In case of Snap it installs apps both through Pamac and CLI without problem but Pamac cannot run nor uninstall packages. Also installed snaps are not to be found in my programs.

Did I mess up something during installation? I found some similar issue here (2). How could I get Flatpak and Snap to work?

Flatpak 1.8.3
snap 2.47.1-1 snapd 2.47.1-1 series 16 manjaro - kernel 5.10.0-1-MANJARO
(1) https wiki(dot)archlinux(dot)org index(dot)php XDG_Base_Directory
(2) https forum(dot)manjaro(dot)org t new-update-made-my-flatpak-apps-disappear 37166