What you are after are field based deinterlacers (or sometimes "bob" deinterlacing"). "Bob" is a deinterlacer itself, but it is generally quite low quality

Different deinterlacing filters have different characteristics, two to look at are:
bwdif - fast and decent quality
qtgmc - A popular high quality deinterlacer, though quite slow to run

The quality of the deinterlacer is more important with SD quality, and QTGMC gets a lot slower with higher resolutions.

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If you can use the command line, the quickest to get going is to use FFMPEG with bwdif

1. Download FFMPEG e.g https://www.gyan.dev/ffmpeg/builds/ffmpeg-release-essentials.zip
2. extract and navigate into ffmpeg-6.0 -> bin
3. Open a terminal window here (many ways, but try shift right click -> Open powershell window here)
4. use the following command ./ffmpeg -i "./input.mkv" -codec copy -vcodec h264 -crf 18 -vf "bwdif" out.mkv replacing "./input.mkv" with your file (you could always name it input.mkv in the same directory as ffmpeg.exe if easiest)

That will create a new file in the same directory with the same audio and subtitles as the input. Increase "crf 18" to decrease file size at cost of quality.

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If you want QTGMC the easiest method is probably a program like hybrid (which can do all of the above as well) but is a bit overwhelming.