I don't believe that's accurate. a lot of instances do have a registration questionnaire required however, mostly to combat spam, similar to some mastodon intsances.
i used roundcube a long time ago too, switched to rainloop, then switched back to roundcube about a year ago. they had just released a new theme (elastic) which also worked on mobile, and seems lighter too. i'm happy with it so far!
the article says it got 3.1 billion in fees, and only 51,600 members (which seems really low). that means each member on average paid around $60,078 in yearly fees? that doesn't seem right?
maybe they meant 51,600,000 members, which then works out to the more reasonable $60.08 in fees?
hugo has recently started using a go-based syntax highlighter that's built in, called chroma i believe (https://github.com/alecthomas/chroma), which is supposed to be much faster than pygments.
anyways, this project looks very interesting to me, i also currently use hugo for my static sites, but this looks much simpler, and the sass compilation is a nice feature too.