[noggin]

Thanks for testing. I only have a couple of 4:2:2 videos, and started re-encoding them to 4:2:0.

Yes - that's my solution for viewing on consumer devices. I also do a w3fdif deinterlace at the same time to retain some of the vertical chroma resolution (4:2:0 1080i25 has half the vertical chroma resolution of 4:2:0 1080p50) - though I think many (all?) Kodi platforms run with a 4:2:0 footprint on playback so may not benefit from it.  I use HEVC/h.265 these days - which is much better with progressive sources than interlaced - hence I deinterlace prior to encoding. (Unlike h.264, h.265 has no PAFF/MBAFF interlace optimisations and just treats interlaced fields separately as if they were progressive frames)

If you don't deinterlace beware the chroma issues of 4:2:2 1080i to 4:2:0 1080i in ffmpeg if you don't deinterlace, as you will need a -filter:v scale=interl=1 or similar to avoid the chroma being treated as p25 rather than i25 (and saturated areas of colour juddering on your re-encode). This is because there IS effectively a vertical scale for the chroma when going from 1080i25 4:2:2 (1080 lines of chroma) to 1080i25 4:2:0 (540 lines of chroma) and that scale needs to be interlaced-aware.