No particular reason to, but if you had to listen to just one of Mulatu's albums, I'd say this is probably 'the' classic: https://mulatuastatke.bandcamp.com/album/mulatu-of-ethiopia
He rerecorded a number of his classics with a band called the Heliocentrics a few years back on a record called 'Inspiration Information'. It's an absolutely amazingly produced record: https://www.youtube.com/watch?v=ZqVhPybzfVE - great sound, great playing.
I've actually played in Mulatu's touring band for the last 11-12 years or so. The thing with Ellington was a State Department tour in the early 70s. I can't remember what they played together (he did tell me the story), but if the Covid travel regulations stay as they are at the moment, we have some gigs next month, so I'll ask. Interestingly, there is some thought that the concert was recorded for the radio, but the tapes are missing - I seem to remember someone saying that they were looking for them (unsurprisingly). [ I've only played on one of his records, but it does include this really great song featuring the totally incredible Fatoumata Diawara: https://www.youtube.com/watch?v=6q0ibCVBFGA]
A couple of Mulatu-related tributaries: the Jim Jarmusch film 'Broken Flowers' features his music very heavily. And also, for hip hop fans, this is a Mulatu sample (the tune is 'Yegelle Tezeta'): https://www.youtube.com/watch?v=OMGd3mAfl-0
Agree with lots of the other recommendations here. Getatchew Merkurya - unbelievable tenor playing. He's also done some really interesting collaborations, including with The Ex. For singers, I agree - two of the iconic figures are Tilahoun Gessesse and Mahmoud Ahmed. And vol. 21 of Ethiopiques for sure - Emahoy's piano playing is absolutely stunning. And like others - I really like Hailu Mergia!