what would happen to distribution X if Canonical suddeny made Ubuntu closed-source?

I believe Linux Mint has done some planning for if Ubuntu does something like that - probably to rebase off Debian in that case

You are correct, distributions like Kubuntu are not TRULY community-driven as they are still subject to Canonical’s influence. Anyone saying otherwise is merely being pedantic.

However it’s not Canonical who’s running Kubuntu, it’s the community, they have the power to revert Canonical’s bad decisions, sadly by giving themselves an increasingly higher workload. Most distributions will simply give up at some point, for example VanillaOS’ next release will be based on Debian as it was getting too tough to remove snap and all the bad things Canonical adds.

Kubuntu uses snaps which are largely disrespected by the community, that’s the end result of being under Canonical’s influence. They can’t rebase on Debian without effectively killing their raison d’etre and they don’t want to remove Snap, perhaps because it would be difficult but most likely because they’re deep under Canonical’s influence, they look up to Canonical to some extent.

This is, in fact, the very meaning of “influence”. It’s even worse, in fact, much, much worse for Fedora, they have been culturally enslaved by Red Hat, sorry for the strong word.

The key is in the name. Whoever distributes the software to you determines whether it’s commercial or community. Where they get it from is irrelevant because they’re the ones distributing it to you.

Ubuntu can’t be made closed-source because of the licensing of the software they use from upstream. Red Hat is still not closed source, for instance. Everyone who gets it gets access to the source code. But if Ubuntu went away or whatever then downstream distributions would be in a spot of trouble. They could rebase on Debian (which is what Ubuntu is based upon), but how hard that would be varies wildly depending on distro. Linux Mint already have a Debian edition, for instance. No problem there. Pop OS would certainly be able to make it work as well; they’re a very professional operation. But take, for example, Endeavour OS. It’s Arch with a graphical installer and some nice defaults. Without Arch Linux (which is almost certainly not going anywhere and is a community distro) they’d have some real problems. There’s no upstream to Arch to rebase on. They’d have to so fundamentally change everything to accomodate a whole new base and packaging system that they’d basically be making a whole new distro.