I have an imac 27 2017 running Big Sur and Lightroom classic all up to date.
When I import files from card I select to sort from capture time. But The files are also sorting by type. Movies, then photos. So I have to pick select the movies from that session. I imagine it should sort all files by the their time.
LR has several bugs reading the capture times of video. Most commonly, LR interprets videos' capture dates as being in UTC (GMT) rather than the local time zone. This will cause videos to sort out of order with respect to photos. These bugs have been present since LR 4 when video was introduced, and it's very unlikely Adobe will ever fix them.