Marvel finally introduced a gay character into the MCU with Endgame, in a short scene with a director’s cameo from Joe Russo. As part of Captain America’s snap support group, the character mentions a date with a new man after his husband was snapped by Thanos.
The moment was underplayed in the extreme, and in some ways it’s great that it was dropped in so casually. There doesn’t need to be special fanfare in universe when a character at a support group mentions his husband.
Let’s be real though - the MCU hasn’t really earned the right to be casual yet.
At least three LGBT* characters have had scenes confirming their sexuality cut, and we are yet to see any queer romance or even 'out' named characters. Marvel has a fair few in their comics to call upon, as well as some characters in the MCU already who could be their first LGBT* superhero.
Eternals will allegedly feature an LGBT character, but if Marvel ducks away from the issue again, there are other characters who could step to the plate. These characters are all potential icons in the waiting, and could provide representation across the board.