Firefox open/save window does not show in flatpak

Make sure `xdg-desktop-portal-gtk` service is working and `xdg-desktop-portal-gtk` is disabled: https://reddit.com/r/flatpak/comments/z5nwhz/how_do_i_get_firefox_to_save_downloaded_files/ldwmadz/

firefox: disable webrtc

1. Go to about:config
2. Set peerconnection.enabled to false
3. Check on https://ipleak.net/

firefox socks5 through ssh proxy

ssh -ND 1080 user@proxyserver