I see this Call for Beta Testing Ubuntu 21.04 and Ubuntu Flavours message and I would like to test this version on my sandbox Linux Desktop (I have another Laptop for work tasks).
I see this old AskUbuntu question How to upgrade to a beta version but as I mentionned here « Software & Updates dialog box doesn't contain "Pre-released updates" option any more »
Question: what is the mainstream process to upgrade Ubuntu from 20.10
to 21.04 beta
?