Selfhosted

I've used both self-hosted Nextcloud, and an instance set up by my school. I have the client on two different Windows machines, and I can confirm the update either tries to kill explorer.exe, which doesn't work half of the time, or forces a restart, so you're not alone with this issue! I also hate the client UI and how it displays conflicted files when multiple people are accessing the same folder. The whole file sync thing feels like a poor attempt to copy Dropbox. My school discontinued Nextcloud support last year because hosting/maintenance took too many resources, they switched to Microsoft i.e. OneDrive and it works much better.

Ok, I'm prepared to be downvoted today so here goes.

Nextcloud is an enterprise cloud suite. The one you run in docker on your rpi (or whatever) is the same one that is run at a company, albeit with more high availability and redundancy, but the same application, proxies, caching, db, etc. Nothing is stopping you from running the stable channel and testing your upgrades, or even rolling out specific stable client versions to your devices.

Said companies often have teams (more than one person) to run it, stage upgrades, automated testing, automated backups, monitoring, etc. They go to work and do just that, maybe not every day but at least a couple times a week their focus is Nextcloud and only Nextcloud.

What many people in the self hosting community do is spin up docker, without ever having touched docker before, and try to run Nextcloud, forget that it exists, and then upgrade it a year later across multiple versions without maintaining the database. Then they obsess about how fast an app loads by refreshing it a whole bunch, and then complain on internet forums that it sucks. This, like many posts, doesn't have a specific problem for us to help with, no logs or stack traces have been posted, and the subject of the complaint shows just how terrible your understanding of application security is.

So, while there is legitimate criticism of some of Nextcloud's design choices, this isn't it. And at the risk of sounding a little gatekeepy, if you post "nextcloud updates break everything" with no context you probably should spend some time gaining a better understanding of how internet facing services work and make an attempt to fix the problem (probably misconfiguration, and in this desktop client case probably a heap of un-updated local software installed alongside the client), which I'm sure people would find if they did the bare minimum of reading a few log files or any of the other things that come with being an application admin.