[HELP] NTSC SD master, best De-Interlace?

[Selur]

So it is always lossless visually

Not always. Running a compression loop will produce compression artifacts since the format is not lossless.

It is professional industry codec.

So is basically any wildly used video format.
Which video format then isn't a 'professional industry codec'?
Just because some NLE uses format X doesn't make it beyond approach good.
A lossy format is a lossy format, 'visually lossless' is just a marketing term.
If you have loss you can make it visible.

Even Apple states:

.. offers visually lossless preservation of the highest-quality professional HD video that a single-link HD-SDI signal can carry

see: https://support.apple.com/en-us/HT202410
They never claimed that their format is always visually lossless, btw. most folks would say the same for H.264 with a rate factor of 13 or below.
Here have been quite a few discussions about what 'visually lossless' really means and as far as I know Apple never gave a statement about it.

Cu Selur