Probably Buffy as well. I'm not even sure what the first show I watched that was exclusively GL focused was, because I watched a lot of them starting from when I was 15. This definitely included some Asian movies, but I couldn't tell you what the first one I watched might be. The first GL series from Asia I watched was Revolutionary Girl Utena, but that's an anime. First live-action GL series (or series I thought was GL) from Asia was Yuri Dano Kan Dano - note that I dropped it and rated it 1/10 once I made my account here.
I've watched several other Asian dramas that had GL elements or subtext, but the first actual GL romance series from Asia I watched was Reverse 4 You. I LOVED that one, but didn't seek out more because my impression (which turned out to be false) was that most of them were on paywalled sites like GagaOOLala (this is bc I mostly heard about Japanese GLs and not ones from other countries).
Then I watched Friendly Rivalry (to date my favorite Asian GL series), completely by coincidence without knowing it had GL elements going into it. And I loved that one so much, I got a little involved with the community around it on tumblr. There was this one user who said it had "more character development in the first ten minutes than in the entirety of The Loyal Pin." I looked up The Loyal Pin bc I was curious what it was; it sounded interesting, and I found out it was free on YouTube, so I watched it (I thought it was decent, though nowhere near on the level of Friendly Rivalry or even Reverse 4 You). Then I checked out the channel and found out it had a bunch of other GLs I could watch for free, and by the time I finished watching those, YouTube was recommending me so much free Thai GL content, I knew I wasn't going to run out.