ID: Drawing of a duck billed platypus underwater, they're wearing a rainbow coloured t shirt and a pink bum-bag, and saying: "Ally is not something you can self-identify as, it's a title that you earn. Let your actions speak for themselves!"
Credit: Sophie Labelle
Hell, you don't even need to be particularly active. Even telling your weird coworker that gay people are people too might help.
You don't get applause for it, but it helps.
I'm not a person with a minority Sexual Orientation/Gender Identity, but here are my two cents: I think upvoting supportive content in a space that's safe and welcoming to people with minority SOGIs is zero impact, online commenting in that same welcoming space is about as impactful as upvoting in a less welcoming space, both of which are directly adjacent to zero impact. I reckon that negatively reacting to an SOGI antagonist (eg the coworker you mentioned), is an appreciable act of allyship, more impact than a token gesture during Pride. I'm not sure if it would be higher or lower than an anonymous complaint to HR about discriminatory language.