[enkimute]

Chris Doran, while not officially in academia, is still very much actively researching these topics and regularly publishes. (he is also a member of the bivector community, very approachable and happy to help out with questions).

Anthony Lasenby, professor astrophysics and cosmology at Cambridge, is also absolutely still actively researching and publishing, all in the mindset of the GA4Physicists book. (See a recent (feb 2020) lecture of him here : https://www.youtube.com/watch?v=x7eLEtmq6PY&t=7s )

(GA4P is considered one of the few comprehensive and up to date treatments of geometric algebra, not just in physics).

[jamessb]

It look like Chris Doran's company was acquired by Arm, and that he is back in academia as a fellow at Sidney Sussex College: https://www.sid.cam.ac.uk/people/dr-chris-doran