He taught classes and and was in charge of their online deep learning materials for a while at deeplearning.mit.edu, back when the idea of universities putting materials online was still very new and cutting edge. A lot of his video lectures are still on his channel.

He made a video on this (https://youtube.com/watch?v=ZlnRlYvPvbs) where he explains he is a research scientist at MIT, but was only active from 2015 to 2020 when he switched focus to his podcast.

He published 15 first author papers during that time period: https://scholar.google.ca/citations?user=wZH_N7cAAAAJ

His research group at MIT: https://lids.mit.edu/people/research-staff

Lex gets a lot of hate, probably mainly for political reasons and the way he manages his public persona. However not many people can argue with the fact he has probably the best collection of programmer interview/podcasts out there. If that's what you're into you probably won't find anything better:

e.g.

Carmack Brian Kernighan Gosling Guido DHH Demis Bjarne

List it endless, and something to be celebrated I think.

See: https://old.reddit.com/r/mit/comments/1m2ewe5/what_standing_...

TL;DR: He is officially listed on MIT site as research scientist, has research published in association with MIT and also did some teaching. However, he does not have any prominence in campus beyond being a media personality and his connection to MIT, while real, is generally considered to be oversold for what it is. Furthermore, Fridman's alma mater is Drexel, not MIT.