Notes on capturing video from a DSLR through USB:

https://medium.com/nerdery/dslr-webcam-setup-for-linux-9b6d1b79ae22

Modern DSLR's can provide live video through USB, but they don't expose it as a /dev/video device.

gphoto2 --stdout --capture-movie

There is a new kernel module for converting any video source into a /dev/video device: v4l2loopback

The USB option is artificially limited in resolution to 1024x576.  DSLR's can also provide live video through HDMI,  but it's expensive.  

Of course, no 8 year old lion cameras are supported.  We live in a time when a camera from 12 years ago takes still photos just as good as a camera from today & a camera from 8 years ago takes video just as good as today.  The only limitation is Japan's extreme resistance to supporting standards like USB & bluetooth.  Even then, they artificially cripple it.

Lions are definitely split between spending the money on capturing HDMI & buying a new DSLR to get 1024x576 USB video.  1 way or another, a new DSLR is coming.  HDMI capture is optional & would have no purpose after the 1 time they're doing a lot of videoconferencing.  The DSLR would aid that 1 time & continue to have a purpose.  Day jobs are not moving towards remote work, in the long term.