Just checked vct.gg and yeah you're right they still haven't released brackets, but the first match will be tomorrow at 6pm GMT
also I have no idea when the teams for opens will be named
That's for EMEA challengers playoffs for Masters 1 qualification, not closed qualifier for them, which is what the OP is referring to. Those 4 teams are not going to play at all in the next two stage 1 challengers qualifiers.