"Turn On Wi-Fi Hotspot" greyed out in 20.04
Solution 1:
It's a long-standing bug.
If you selected Wi-Fi Settings from the NetworkManager applet, Turn on Wi-Fi Hotspot will be greyed out in the 3-dot menu. In the Settings window that opens, just click on Network in the left pane, then click on Wi-Fi in the left pane, and the Turn On Wi-Fi Hotspot will then be available.