The problem is that most normal people (HN is not normal - mostly for the better) don't even understand what sideloading is - let alone actually care.
How can we fix this?
(aside from making people care - apathy enables so many political problems in the current age, but it's such a huge problem that this definitely isn't going to be the impetus to fix it)
Off the top of my head there's a Debian based one, a Fedora based one, webOS, PostmarketOS, probably others. Wouldn't be that difficult but yeah, the cost of entry is still probably tens of millions.