U2 will perform next week on ABC's late-night show Jimmy Kimmel Live. Kimmel himself announced it during his show tonight (Thursday):
Next week on the show we have brand new shows... (announces non-musical guests) ... music from Bush, Zac Brown Band and Lil Yachty. And U2 will be here in celebration -- this is going to be very, very exciting -- of the 30th anniversary of The Joshua Tree album. So please join us for all of that.
Although he doesn't specifically say U2 will perform, including U2 in the list of musical guests is a signal that they will.
Ironically, we were chasing down this rumor today, posted the rumor on Twitter and then Kimmel made the announcement on air about 10 minutes later. We've heard the band will perform two songs and that it'll happen on Kimmel's show next Tuesday, May 23. That's a day off on the Joshua Tree 2017 tour, but just a day before U2 performs in Houston.
U2 has never appeared on Jimmy Kimmel Live, but Bono has participated in two (RED) Shopathon fundraisers during Kimmel's show.
UPDATE, May 19: Variety.com confirms that this'll happen on Tuesday, May 23, and also quotes a hard-to-find news release that says U2 will do an interview and perform on the show: "...their only sit down TV interview and performance while on the road in the U.S. for The Joshua Tree Tour 2017."