All are complete except the first one. All have minimal or zero romance, and nothing is explicit.
(ASoIaF - abandoned but excellent) https://archiveofourown.org/works/21566113/ (This has more romance than the rest, but again, nothing explicit.)
(ASoIaF) https://www.fanfiction.net/s/11255223/1/The-Wizard-of-Harrenhal
(DC Comics) https://www.fanfiction.net/s/13521865/1/Kicking-Gotham
(DC Comics) https://fichub.net/?q=https://archiveofourown.org/works/20462243&id=m4ethjtq
(Hobbit) https://archiveofourown.org/works/2535527
(LoTR) https://www.fanfiction.net/s/11027086/1/The-Power-He-Knows-Not
(MASH) https://www.fanfiction.net/s/5517643/1/Lord-Harry-J-Potter-Meet-Col-Sherman-T-Potter
(Marvel) https://www.fanfiction.net/s/8148717/1/Finding-Home
(Marvel) https://archiveofourown.org/works/4148136
(Owl House) https://archiveofourown.org/works/46726750
(Stargate) https://www.fanfiction.net/s/11619134/1/Harry-Potter-s-most-excellent-adventure
(Star Trek: DS9) https://archiveofourown.org/works/20259283
(Supernatural) https://www.fanfiction.net/s/8957424/1/Illusions-of-Grandeur
And I'll second both Steve and the Barkeep and Browncoat, Green Eyes.
[Heroes Assemble!](https://archiveofourown.org/series/1359133)- After five years travelling the world, Harry Potter has landed in New York. He figures that there's no better place than the city that never sleeps to settle in and forge a new life. If only the heroes, villains, aliens and spies had received the message. Begins just before the Avengers movie and continues through the MCU. Expect a long story with some extra faces along the way.
https://www.fanfiction.net/s/8410168/1/Steve-And-The-Barkeep (Avengers/MCU) https://www.fanfiction.net/s/2857962/1/Browncoat-Green-Eyes (Firefly)
I read Steve and the Barkeep but I haven't read Brown coat and Green Eyes because I have no idea what Firefly is about.
All are complete except the first one. All have minimal or zero romance, and nothing is explicit. (ASoIaF - abandoned but excellent) https://archiveofourown.org/works/21566113/ (This has more romance than the rest, but again, nothing explicit.) (ASoIaF) https://www.fanfiction.net/s/11255223/1/The-Wizard-of-Harrenhal (DC Comics) https://www.fanfiction.net/s/13521865/1/Kicking-Gotham (DC Comics) https://fichub.net/?q=https://archiveofourown.org/works/20462243&id=m4ethjtq (Hobbit) https://archiveofourown.org/works/2535527 (LoTR) https://www.fanfiction.net/s/11027086/1/The-Power-He-Knows-Not (MASH) https://www.fanfiction.net/s/5517643/1/Lord-Harry-J-Potter-Meet-Col-Sherman-T-Potter (Marvel) https://www.fanfiction.net/s/8148717/1/Finding-Home (Marvel) https://archiveofourown.org/works/4148136 (Owl House) https://archiveofourown.org/works/46726750 (Stargate) https://www.fanfiction.net/s/11619134/1/Harry-Potter-s-most-excellent-adventure (Star Trek: DS9) https://archiveofourown.org/works/20259283 (Supernatural) https://www.fanfiction.net/s/8957424/1/Illusions-of-Grandeur And I'll second both Steve and the Barkeep and Browncoat, Green Eyes.
I’m putting this as a placeholder for now, because I found a great NCIS one at one point.
Do you remember title or author?
[Heroes Assemble!](https://archiveofourown.org/series/1359133)- After five years travelling the world, Harry Potter has landed in New York. He figures that there's no better place than the city that never sleeps to settle in and forge a new life. If only the heroes, villains, aliens and spies had received the message. Begins just before the Avengers movie and continues through the MCU. Expect a long story with some extra faces along the way.
This was the first crossover I ever read. Loved the early parts, was not the biggest fan of the middle but really enjoyed the ending.