If you run endeavour, you are basically getting Arch with a familiar installer, a few useful helper scripts, and a friendly community. You are still expected to know your hardware and your install. You are still expected to keep up with the Arch news, and make any manual interventions required. If you do that, endeavour is remarkably reliable.

I’ve been running it for a long time without issue. But how “stable” it is depends on how much you read the documentation and developer announcements, and how much you fiddle with things you don’t understand. That can be true in mint or Ubuntu as well, none of them prevent you from breaking things.

Recently endeavour changed the way they deal with some firmware related packages, this would cause an error when updating, causing a handful of packages to not be upgraded. A quick DuckDuckGo search of the error message took me straight to a forum post by the devs explaining that you have to uninstall one of the related packages, and run the update again. If you didn’t think to look you’d probably panic and think your system was broken. Just an example of how the operating system itself doesn’t hold your hand. It’s up to you whether that’s acceptable or not.

On the topic of stability, save your important files on a separate drive. It’s been said elsewhere in the thread but bears repeating. As long as your files are stored in a separate drive, if you run into issues you aren’t able to fix, you can just wipe and reinstall, it maybe takes 20 minutes depending on your hardware, and while you’re experimenting and learning, it wouldn’t be uncommon for you to break some things.

Operating systems are rarely unstable. Users are the most common source of instability.