My SME froze every time I wanted to open a workspace. This issue was related to a similar one in chrome and firefox - when I tried to upload an attachment, the opened dialog to browse my files froze and the browser needed to be restarted.
The error in console showed the following:
Can’t open portal file chooser: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name org.freedesktop.portal.Desktop was not provided by any .service files
Using this command helped in the end 
sudo apt install xdg-desktop-portal xdg-desktop-portal-gtk