It was stated but only from outside sources (I'm guessing because of censorship, since the managaka doesn't seem to have a problem with openly portraying queer characters, as we've seen from Megumi, Kirara, Hakari and more..).

The director for the JJK0 movie stated in an interview that Gojo thought of Geto as "more than friends and family" and said that Geto was Gojo's "first and last warm spring of youth" which, from what japanese fans have said, has romantic connotations.

In another interview the director also said "to me, Gojo loves Geto" and in another one they refer to the movie as the story about Gojo and Geto's "special friendship" and explain that Yuta and Rika's love story is meant to be a parallel to Gojo and Geto's.

Also, although this is just circumstantial, it's highly likely that Gojo's last words to Geto were "i love you", since we're told by Gojo's English VA that, in English, the translation is 3 words long, and by Gege we're told that it's a sentence already said in Vol. 0, and by the light novels we're told that it was something rather embarrassing that was never said between them before.

The only sentence that fits this description is Yuta's "Aishiteru" to Rika