Profile Sync Daemon config for Vivaldi Flatpak
Create the file /usr/share/psd/browsers/vivaldi-flatpak and add the following contents:
if ! flatpak override --user --show com.vivaldi.Vivaldi | grep -q "/run/user/$UID/psd"; then
flatpak override --user com.vivaldi.Vivaldi --filesystem=/run/user/$UID/psd
fi
DIRArr[0]="$HOME/.var/app/com.vivaldi.Vivaldi/config/$browser"
PSNAME="$browser"-bin
Add Vivaldi Flatpak to ~/.config/psd/psd.conf:
BROWSERS=(vivaldi-flatpak)
Restart psd.service.
systemctl --user restart psd.service