The Suspend Button extension is officially supported up to GNOME Shell version 3.34 whereas Ubuntu 20.04 has version 3.36.x. So rather unsurprisingly it doesn't work on Ubuntu 20.04.
On Ubuntu 20.04 you'll find the suspend option hidden under the 'Power Off / Log Out' option in the system menu:
The Suspend Button extension is officially supported up to GNOME Shell version
3.34whereas Ubuntu 20.04 has version3.36.x. So rather unsurprisingly it doesn't work on Ubuntu 20.04.On Ubuntu 20.04 you'll find the suspend option hidden under the 'Power Off / Log Out' option in the system menu:
Alternatively, you can search with the word "suspend" in Activities or applications overview; refer to this answer from Where is the suspend/hibernate button in GNOME Shell?