Wasn’t OP complaining about the Windows desktop client? What has that to do with the server setup, Docker, etc? People can have the exact same issues on the client side even if the Nextcloud instance is professionally managed by a large organization.
I use a folder structure in Nextcloud where each “album” folder starts with YYYY-MM-DD so I can sort them alphabetically. I delete the photos from my phone when I copy them to the Nextcloud folder. I can always look them up using the app. This is some manual work, but it has worked very well for long-term archival and it will still be organized and searchable on other platforms as long as they support files and folders.
For Kanban I use wekan, because it has more features. Nextcloud I host using snap, which I cannot 100% recommend because it sometimes has troubles upgrading to the latest version. Still, for me it causes less trouble than a manual install.
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.