I almost invariably need to convert the files I work with into a format that DR understands. These are MP4 from GoPro, DJI Mavic Pro and from a Panasonic TZ60. Unconverted files simple never show up at all in the media bin, they do AFTER conversion and then they're fully functional, i.e. they have proper preview etc.
I'm no CODEC expert, but I use ffmpeg (free software) to convert it to a PRORES codec. While that works well, the files you get after conversion are gi-normous, which creates a bit of a challenge keeping multiple projects around and even saving them for later use.
Perhaps someone can suggest a format that works but isn't quite the volume of PRORES?
There are a bunch of examples on this page here:
https://duduf.com/easily-transcode-any-media-to-any-format-using-ffmpeg/I haven't quite worked out what the conversion does to embedded timecodes. I haven't looked into it that much, but I think that ffmpeg can embed them during the conversion too.