What do you mean with “Operating System”?

It is most often installed as Docker container, which isn’t an OS, but just includes all dependencies to run. You still need an OS (like Debian) as host.

I use Casa"OS". It’s fine, but nothing groundbreaking. Cockpit for example can do pretty much the same, and for Docker containers, I nowadays mostly use docker compose.

But hey, it helped me a quite a bit in the beginning, and it’s cool. Pretty basic, but enough for most people, mainly beginners.

Logseq and Obsidian are only similar on the first look, but very different usage wise. Both are very open with a plugin system, and you can modify them to turn them into one eachother.

So, if you want only FOSS, then Logseq is the only choices you have.

But Obsidian is, even though it’s proprietary, very sane. Open plug-in system, active community, great devs who don’t have much against FOSS, and more.

Obsidian

• More similar to a classic note taking app, like OneNote, but with a lot of features. Hierarchical structure, and more of an “essay” style, where you store a lot of text in one page.
• Page linking is only done when you think it makes sense
• Has been a bit longer around than Logseq, feels more polished
• Great sync and mobile app, which support plugins from what I’ve heard

Logseq

• Non-linear outliner. Every page is on the same level, but within a text passage, the indentation matters (parent-child-relationship)
• You create a LOT of more pages. Most of my pages are empty. They are mainly there for linking topics. I rarely create pages manually.
• The journal is where you write most stuff. You then link each block to a page.
• Logseq a bit “special”. May not be for everyone. I for example am a bit of a disorganised thinker, who mentally links a lot of knowledge and throws concepts around all the time. Logseq is my second nature, because it’s more flexible. My GF on the other hand is more structured, and prefers something like Apple Notes, or, if she would care about note taking, something like Obsidian.
• The mobile app isn’t great. It’s fine when I’m not at home, but the desktop version is the “proper” one, and mobile/ iPad a second class citizen.
• Sync is only experimental for now. It will soon be officially supported (hopefully) and self hostable, but it worked fine for me.

I don’t see any problems with that. Even I (and probably most others here), who are FOSS advocates, think Obsidian’s model is fine.

The devs surely get why FOSS is important, and try their best to match the pros of open source. They even stated that if the company goes bankrupt or they stop developing the app, they’ll open source it.

One major thing they do absolutely right is how the notes get stored. On other note taking apps, it’s a proprietary database, often “in the cloud”, where your notes get hold hostage. Here, they’re just Markdown files, and the whole thing is pretty open, encouraging a strong community.

It’s similar to Valve/ Steam. Proprietary, but liked by most Linux people.

Logseq! Right now, you can only self host the database and sync it with Syncthing for example, but the dedicated sync feature is currently in beta and will be self hostable afaik.

Grocy is exactly what you asked for.

I never had any (major) problems with Nextcloud yet.

I just have following “conflicts” with it:

• It doesn’t follow the “Do one thing, and do it right”-philosophy. It tries to do everything at once. File upload/ sharing, media management (NC Photos), RSS, mail, calendar, contacts, and much, much more. I mean, it’s damn convenient and works pretty fine, but nothing is great. For example, Immich/ Photoprism is way better than NC for photo management.
• There’s a lot of abandonware, or buggy/ unmaintained apps. For example, my “News”-feed looks completely broken for months now.
• The performance isn’t good. I mean, the “server” (an old thin client) isn’t fast at all, but the loading times and responsiveness is just awful. The file upload also takes ages, even from the same network.
• It feels bloated. I think, if I would be more into selfhosting and had more time, I would search for alternatives and split all the NC features I use into their own services, e.g. one for file upload, one for document management, one for managing my photos, an own RSS client, and more.

But, as I said, the ease of use and amount of features is still great. I don’t want to spend three weekends just troubleshooting my server and searching for/ installing dozens of individial services. And for that, it’s good enough.

If you have a spare laptop/ PC, I insist you to try Nextcloud.

It’s super easy to install, you actually just download the Docker all-in-one container and it runs in less than 10 minutes. You don’t have much to loose.
I’m relatively happy with it.

I mean, to be fair, NC isn’t perfect. It sometimes feels a bit wonky and tries to do everything, while exceeding at nothing.
But it’s damn comfortable to set up and maintain.

It doesn’t perfectly cover your use case, but everything else (individual services, including web server, database, etc.) is less centralised and more complicated to set up.
Since NC AIO is inside a container, all data are too. It’s a relatively straightforward file system afaik.
Backup also is included, but you have to do it manually by default and it stops the services while doing it.

For offloading large files, you might look into 3rd party tools. NC is basically a remote drive you can connect to with most programs that support it.