Hi Duncan,
If you chose to install the wifi hotspot with RACHEL, it sets the whole thing up to act as a hotspot for users to connect to. Changing anything related to the wifi after that using the Network Manager UI is not suggested. You’ll need to use LAN to connect to the internet while RACHEL is configured with a hotspot enabled.
The alternative is to select the option where RACHEL doesn’t install a hotspot during the installation. That way you can use the wifi normally.
James