How to start Brave in "Kiosk" mode on Ubuntu?


Description of the issue:
How can this issue be reproduced?

1.I have to set up an ultra-secure, ultra simple laptop for an elderly relative who can no longer navigate Facebook to accept incoming video calls from the family, My thoughts were to use an absolutely minimal version of Ubuntu and start Brave full screen on power up. The intention being that there is nothing to confuse - this laptop is only for relatives to open a meet.ji.si room to chat with an elderly scared old lady who cannot get the visitors she needs cos COVID, so no obvious way to go browsing, no other apps apparently available cos Brave is full-screen.
Other than being non-fullscreen, this seems to work adequately.

Expected result:
Brave opens fullscreen on startup at the required meet.ji.si location

Brave Version( check About Brave):
1.26.74 Chromium: 91.0.4472.124
Additional Information:
Ubuntu 20.04 LTS all updates applied