I am still learning my Osmo Action.
I wonder what frame rate should I use? - I shhot mainly HD 1080p.

What do you use? Why?

What would you recommend to use?

Id start with 24fps

For sport and action activity shot in 60Fps

Thank you for asking for recommendations, we really need to know what you like doing so we can tell you what to use.

We do not know you are  a PAl or NTSC so like said Sports is 50/60 fps, Cinamtic is 24/24 fps. Low level shots are lowest FS.  fast motion and blur are higher fps and well shutter speed, etc so on.

You seem to be in Europe and the broadcast system there is PAL, so to conform to your local standards 25 or 50 should be your first choices.

Movies are traditionally shot at 24 fps, and that frame rate gives your footage a so called "cinematic" look, compared to a "home movie" or "tv show" one. It also allows slower shutter speeds in low light conditions  as you only need 24 frames each second; providing a noise advantage utilizing lower ISOs.

50 or 60 -depending on your region- will give you more fluid motion not only because they record much more information (technically you double your temporal resolution) but also because you are more likely to be closer to ideal shutter speeds (180 degree rule) at those frame rates; especially outdoors without ND filters.

In the end it all boils down to personal priorities and preferences.

Hope this helps...

I shoot 60 fps for action and 24 fps in low light or indoor when no action involved.
25 or 50 fps is only if you plan to show the video on a TV here in Europe.