So, OP's claim that Lenin "legalized homosexuality entirely" in the USSR is wrong because, as @sorrybookbroke@sh.itjust.works pointed out, it remained illegal in some parts of the USSR, such as Azerbaijan, Georgia, Turkmenistan and Uzbekistan. Therefore, it was never entirely legalized across the entire USSR until Stalin banned it entirely again in 1934. During that decade, homosexuality was only legal in the RSFSR and not because of a standalone law advocating for sexual freedom, but because the Tsarist legal codes were abolished (which also included abolishing the Senate, the Tsarist courts and the private property, which were more likely to be the target of this move) without introducing a specific ban in the new legal code.
So it's also misleading to claim that homosexuality was legalized like it was an intentional move towards sexual freedom (which Lenin cared very little about with no public record of him on this topic) instead of just the kind of accidental outcome of abolishing the Tsarist legal codes.
Even if everything else were true, the USSR still wouldn't have been the first country to legalize it in modern history, which was France in 1791.
https://libcom.org/article/notes-early-soviet-attitudes-homosexuality

Threema is free as in free speech, just not free as in free beer: https://f-droid.org/en/packages/ch.threema.app.libre/