What other Exorcist sequels are there?

Believer picks up the story of 1973’s The Exorcist, ignoring the existence of John Boorman’s Exorcist II: The Heretic, which brought back Linda Blair as Regan and has somehow dodged much cult adulation—a miracle considering how completely wild and bonkers it is (read io9’s retro review here). Exorcist director William Friedkin famously told the HuffPost that is was “one of the worst films I’ve ever seen … I find it worse than terrible; I find it disgusting.”
On the other end of the spectrum, Believer also discounts the excellently eerie The Exorcist III, written and directed by Exorcist author William Peter Blatty (adapted from his 1983 Exorcist sequel, Legion; he’d previously won an Oscar for adapting his novel for the original film). It takes place in Georgetown and finds a way to bring back Jason Miller as the very much deceased Father Damien Karras, with George C. Scott stepping into the role of Lieutenant William F. Kinderman, another character from the 1973 original. It also contains maybe the most unforgettable jump scare scene in all of horror. (io9 also has a full retro review on part three.)
And, of course, there was the Exorcist TV show, created by Jeremy Slater (Moon Knight, The Umbrella Academy, Godzilla x Kong: The New Empire). It ran for two seasons across 2016-2017 on Fox. The first season featured Geena Davis playing a character eventually revealed to be Regan MacNeil living under an assumed name; the second season brought season one’s priest duo (Ben Daniels, Alfonso Herrera) into a new spooky mystery. It was a really good, genuinely freaky show!