Actually, my thoughts over the past week have mostly been obsessed with the journal Nový hlas, which was published from 1932 to 1934. This riveting publication, subtitled List pro sexuální reformu, seems to have been the main voice of the interwar Czechoslovak gay rights movement, though it was preceded by Hlas sexuální menšiny, which I have not yet seen.
Thanks to Nový hlas, I now know where all the happening gay clubs of the day were located. City Dancing at Templova 1, Prague I, invited readers to enjoy “comradely fun”, beer, boxing, and dancing in a homelike, cozy place run by Kamil, formerly of the gentleman’s club and restaurant Batex. Batex (Revoluční 1, next to palác Kotva) described itself as a gentleman’s social club open all day until 3 a.m. with evening singing, music, dance floor, excellent food and the best drinks. The Casino restaurant at Ječná 10, Prague II, claimed that “the best friends rendezvous” at it, and offered a jazz orchestra and dance floor (illustrated by a drawing of a flirtatious pair of uncertain gender). And there were quite a few others, all apparently in Prague. If there was anything in Brno, Olomouc, Ostrava, or Bratislava, it did not advertise in Nový hlas.
Did members of the avant-garde visit these clubs? Well, I suppose it depends on which avant-gardists one has in mind. I haven't seen any guest lists.
Do I know more defunct 1930s gay clubs than present-day ones? Indubitably. On the other hand, I wouldn't say I don't know the names of certain present-day establishments. More to the point, at least I know where to ask.
Postscript: I have discovered that Stud Brno has a story on the First Republic situation at Postavení homosexuálů v ČSR v letech 1918 - 1938. The article is in several parts.