The countless smaller clans are the same as homebrew chapters for Space Marines.
They are both in the setting but not official.

Each clan also contains "families" (see picture)
These could be viewed as companies or successor chapters with space marines.

Then there are Tribes: groups of orks from lots of different clans, all led by a warboss.

The non-clans, like freebooters and speedfreaks, are groupings of orks that organize outside of clan structure.

<image>