Permissions problem with some of snap packages after updating ubuntu from 20.04 to 22.04

Hi. After upgrading Ubuntu (20.04 -> 22.04), some of packages, and first of all Firefox (whose default package manager was forcedly replaced from apt to snap in the new Ubuntu) get problems with permission rights. For example, I cannot save any downloaded files from Firefox in any directory. Also, I cannot install new extensions (although my settings and extensions from the previous installation have been kept) or cannot choose Firefox as the default browser. Similarly, in telegram-desktop and chrome I cannot upload/download files from default ~/Downloads (although other directories are accessible for these snaps, unlike Firefox). If I create a new system user which did not exist in my system before the upgrade, everything though works ok for that user. Please help

Can you provide the output of snap connections firefox ?

Hi, yes sure.

Interface                 Plug                            Slot                             Notes
audio-playback            firefox:audio-playback          :audio-playback                  -
audio-record              firefox:audio-record            :audio-record                    -
avahi-observe             firefox:avahi-observe           :avahi-observe                   -
browser-support           firefox:browser-sandbox         :browser-support                 -
camera                    firefox:camera                  :camera                          -
content[gnome-3-38-2004]  firefox:gnome-3-38-2004         gnome-3-38-2004:gnome-3-38-2004  -
content[gtk-3-themes]     firefox:gtk-3-themes            gtk-common-themes:gtk-3-themes   -
content[icon-themes]      firefox:icon-themes             gtk-common-themes:icon-themes    -
content[sound-themes]     firefox:sound-themes            gtk-common-themes:sound-themes   -
cups-control              firefox:cups-control            :cups-control                    -
dbus                      -                               firefox:dbus-daemon              -
desktop                   firefox:desktop                 :desktop                         -
desktop-legacy            firefox:desktop-legacy          :desktop-legacy                  -
gsettings                 firefox:gsettings               :gsettings                       -
hardware-observe          firefox:hardware-observe        :hardware-observe                -
home                      firefox:home                    :home                            -
joystick                  firefox:joystick                :joystick                        -
mpris                     -                               firefox:mpris                    -
network                   firefox:network                 :network                         -
network-observe           firefox:network-observe         -                                -
opengl                    firefox:opengl                  :opengl                          -
personal-files            firefox:dot-mozilla-firefox     :personal-files                  -
removable-media           firefox:removable-media         :removable-media                 -
screen-inhibit-control    firefox:screen-inhibit-control  :screen-inhibit-control          -
system-files              firefox:etc-firefox-policies    :system-files                    -
system-packages-doc       firefox:system-packages-doc     :system-packages-doc             -
u2f-devices               firefox:u2f-devices             :u2f-devices                     -
unity7                    firefox:unity7                  :unity7                          -
upower-observe            firefox:upower-observe          :upower-observe                  -
wayland                   firefox:wayland                 :wayland                         -
x11                       firefox:x11                     :x11                             -

The interfaces appear to be connected. Perhaps it’s something with portals again. Maybe @oSoMoN has some ideas.