Not familiar with the nextcloud side of things, but I just pulled all my photos from Google photos and imported them all to Immich. I'd imagine if you just have a folder full of images, it'd work the same way. During the Immich setup, you can designate an import folder. Point that import folder at your photos folder that you want to bring in. Once you have Immich up and running, you can use the terminal and run an import from the command line on that import folder. You'll have to make an API key for the CLI to use, but you can make that in the settings. Immich doesn't currently support mass importing from inside the UI, so this is the only way I've found to do it. The import ran fast for me though, went though 125gb of photos and videos in about 5 mins.
Switching from Google photos to immich was one of the best uses for server I've ever implemented. Amazing piece of software and one of the best open sources projects in a long time
Alternatively you can just use external library and point it to nextcloud photos folder. That way you can't edit or delete files in immich, but you can see them just like any other picture. I upload everything from my phone to immich, but still have some folder organized photos in nextcloud.
Don't mind him. He's always there ranting about who knows what whenever software he dislikes is mentioned. Lookup his comment history for more of the same.
Easiest method to summon him is to mention Nextcloud and Proxmox in the same sentence.
Not OP but I found nextcloud to be incredibly buggy and resource intensive when I had it spun up. Now, I had it spun up on top of TrueNas Scale which its own bucket of shit, but I digress. Pushed me to just using discreet services for everything and I like it much better.
I used it for a few years, but it broke a few times, and I had to search online and find an occ command to fix it. It also could break if you didn't upgrade regularly and skipped versions. Or you upgraded too quickly before a bug was hotfixed.
Maybe it is better now, but I looked into alternatives and found syncthing to be awesome (after I switched from iphone to android). I use samba share for cold storage. Syncthing can take a lot of space since it syncs all the files to all units
Dunno about him, but for me I forget to update it and then when I remember it can't update because its so out of date it cant resolve something or other, and I end up having to just reinstall the latest version and jump through hoops to get the users files to show up, and then one time before as well as the most recent one that made me give up database problems occurred and I don't know how to database.
The better question is, what's NOT wrong with Nextcloud?
Nextcloud is also a perpetually half made project that breaks at every corner and requires a lot of resources. The sync works until you add like a TB of small files and it never works fine again, unlike Syncthing that can handle whatever you need. Also unlike FileBrowser the WebUI is slow at listing files and related operations. The webmail is yet another pile of JS errors and nonsense idiotic stuff like being unable to show a bullet list.
The Android app is garbage, often refuses to automatically synchronise, and for the past few releases has been displaying an error saying it can't connect to the server even though it clearly can.