[noggin]

25Hz to match 25fps half motion deinterlacing is not equal to Amcodec full motion 50fps deinterlacing like you would get on say a AMLogic LibreELEC box.

Exactly. Any interlaced source should be deinterlaced to twice the interlaced frame rate (29.97->59.94, 25->50) to preserve the motion on native interlaced content (i.e. stuff where there is motion between two fields in a frame)

If you deinterlace to 29.97p or 25p you are completely wrecking any native interlaced content and making sport, entertainment, news etc. content essentially unwatchable juddery.

25fps half motion is rubbish for fast action sports viewing. TV's motion interpolation causes all sorts of issues with such a low frame rate.

TV Motion Interpolation should cause no issue BECAUSE IT SHOULD ALWAYS BE DISABLED! Otherwise you are just watching a car crash of guesstimation and have absolutely no idea what any source you are watching is actually doing.

Mpeg2 deinterlaced output is also blocky as well vs high quality Amcodec hardware deinterlacing.

What do you mean? MPEG2 is the source codec. Not sure what you are trying to say. Irrespective of your viewing platform and MPEG2 interlaced source is an MPEG2 interlaced source.