flameshot error: Screenshot portal timed out after 30 seconds

On a linux (arch or gentoo) with xfce4 and X server, flameshot does not run and gives an error:
flameshot: error: Screenshot portal timed out after 30 seconds
flameshot: error: Unable to capture screen

To fix that:
mkdir -p ~/.config/flameshot
Create or open if exists, ~/.config/flameshot/flameshot.ini, and add to it
[General]
useX11LegacyScreenshot=true
Restart flameshot