Is it possible to get GNOME Shell 'Activities' Overview to show windows from all Workspaces?
Solution 1:
Yes it is possible with this Overview all windows extension.
Although it won't work after install, download the schemas folder from its git repo and paste in extension folder.
Path of extension folder:~/.local/share/gnome-shell/extensions/OverviewAllWindows@amiller27
Overview shortcut will be super+ctrl+tab.