This is an interesting piece of history!
Fortunately I found something about it on the net.
Reichsjugendtag only means that it was a Germany-wide meeting of the youth.
It was clear to me that it could not be HJ. It is rather the opposite: left-wing workers' youth. Namely the
Sozialistische Jugendverband für die deutschen Gebiete der Tschechoslowakischen Republik/Socialist Youth Association for the German areas of the Czechoslovak Republic, founded in December 1920 (as the remaining remnant of the Sozialistische Arbeiterjugend SAJ/Socialist Workers' Youth after the split from the Communists). It is thus the youth organisation of the Deutsche Sozialdemokratische Partei in der Tschechoslowakei/German Social Democratic Party in
Czechoslovakia (DSAP). This 2nd Reichsjugendtag took place in Aussig on 27 May 1928. After the Anschluss/annexation of the Sudetenland, this organisation was banned.
The motif is by the artist Victor Slama.