fact one: country flags in Unicode are just 🏳️ combined with Regional Indicator Symbols (or in the case of constituent countries of the UK, tags) using a zero-width joiner.
fact two: 🏳️🌈 and 🏳️⚧️ in Unicode are just 🏳️ combined with 🌈 or ⚧️ respectively using a zero-width joiner.
conclusion: according to the Unicode Consortium, gay people come from a country that can be shortened to 🌈 and trans people from a country that can be shortened to ⚧️.