I can recommend a full-frame Canon RP ($999) with RF 35mm f1.8 lens ($449) as a relatively inexpensive narrow FOV setup.
Edited to add: Meant Narrow DOF when writing this, but both are true if you sit close to it!
Edited to add: Meant Narrow DOF when writing this, but both are true if you sit close to it!
If you expect someone to sit for 8 hours a day give them a good chair lest they start having back issues after two months of employment.
My other thought is that the suggested lens can stop down to f1.8, which would give a nice narrow depth of field (DOF) and add a pleasant background blur, but it would also be harder to stay in focus during a call. If the person on camera moves forward or backward very much at all when the lens is at f1.8, they would be pretty blurry. So perhaps they could get away with a lens that just stops down to f2.8 or so, albeit with worse low-light performance (smaller aperture, less light coming through).
But take these comments with a grain of salt. It sounds like you have a setup that works well for you.
In any case I find if you sit close to your camera, 35mm is a good FOV that will fit in your head and shoulders. The background blur for f/1.8 works well if you enable Servo Autofocus with Face Detect. It will momentarily get confused if you step out of the frame and back in again, but it can track a face pretty well after that.
On full frame I used 85mm 1.8 to get a a good FOV / DOF / proportions.
But it sat on a tripod 1.5 meters behind my computer and made the room a nightmare to navigate :D
35mm on FF would indeed be mildly wide (just on wide side of "normal" 50mm lens)
That said, even the greatest autofocus isn't going to be able to keep up with a person who moves around a lot at f/1.8 - so it's reasonable to stop down a bit if that's the case for your subject.
The mirrorless EOS camera's (R series) have autofocus with face tracking which works quite well. At f1.8 you get 8cm depth of field at 1m distance so you'd have to stop down the aperture to about f4 if you want your whole head to appear sharp on video.