What do you mean group series together? If you mean seasons of a show, yes it does. If you mean collections, it has them.

Then I could not figure how to make it work. Plex did that without any effort from my side though

First hit on google: https://jellyfin.org/docs/general/server/media/shows/

Thanks, I can google. For some reason Jellyfin totally ignores folder structures for me.

Actually after reading it more carefully I probably see why it didn't work for me, but the notes in the page are bizarre:

* Avoid special characters such as * in M*A*S*H, use MASH instead.

Since when a common ASCII character is a special one? What about more common unicode characters I use?

* Do not abbreviate the Season folder with S01 or SE01 or alike.

I.e. if I put anything not in the folder named "Season XX" it won't work? Ugh... really?

* Season folders shouldn't contain the series name, otherwise Jellyfin can in certain cases (Stargate SG-1 due to the dash and one, for instance) misdetect your episodes and put them all under the same season.

Well, how about to fix it?

* Episode numbering for specials may vary from metadata provider to metadata provider.

Very helpful, so the "Series XX" required above won't always work.

And even if everything above fails why not to sort by name? It should not be hard for any engineer, right?

What do you mean random order? You can choose the sort order for any library yourself.

I have one folder with movies and series. It shows as a randomized mix, maybe it uses something like modification time by default? It's definitely not by name.

In my experience you have to sort shows into directories and sub-directories for a series.

My entire jellyfin library is just symlinks into where my crap has accumulated over the years.

https://jellyfin.org/docs/general/server/media/shows/

I have the series in their own folders. I tried to do a more nested structure to no avail. After a day of attempts to fix it I switched to Plex and it despite having its own quirks just worked fine.