Only the 21” iMac has gotten Apple Silicon, so it makes sense that...
Actually, I have a 24" iMac with the M1 chip.

Never mind! I found several options.

Q: is there an easy adaptor so you can use an SD card to import video footage and still images?

This is really well done, Joe, and I know this because I have written similar things about friends who have passed. You can always know sincerity when you hear it, and your friendship with Dave is apparent. Any given person only comes into contact with so many people with whom they connect on a deep level, so your loss has to be huge. Prayers to Dave, his family, and friends, as they grieve his death.