I am uninterested in purchasing proprietary hardware running a proprietary operating system that'll work (maybe) for some amount of time. Sure, it's technically self hosted. But you can't extend it (without their proprietary app store). It doesn't seem like you can write your own apps without registering, or side load them. Details are extremely thin on the site, so let me know if I'm wrong.

Hell, all the compelling software isn't even theirs! They're just running other OSS apps, and god knows whether you'll be able to manage or upgrade it.

Arguably, this is the worst of all worlds: you're paying the overhead of closed hardware, running closed software that you don't control, and sort of just crossing your fingers that they don't pull the rug out from underneath you. You'd be infinitely better off buying a comparable NUC and spending an afternoon loading up Docker on it. Shit like this is genuinely insulting to the demographic of folks who should be the target audience.

Have things changed drastically? I have an Umbrel instance running on an x86 server at home. When I installed it, it was fully open source, open API, and free.

There's a Github link for the os, but it is under some strange not-quite OSS or Free Software license... https://github.com/getumbrel/umbrel

This reads like a laundry list of assumptions rather than facts

I had one of those systems years ago (don't remember the name). Used it for a while, then one day they just disappeared and my "personal cloud" was a "personal brick".

In what way is the proprietary? It looks to be just a PC box running OSS apps?