Send language preference to groupchat server
There is no way in Gajim to configure a language. The "configure room" form text appears in the conference server's default language.
I have tried setting a language preference in the 'Jeti' jabber client, and testing with conferences on conf.netlab.cz public groupchat server. With the language preference 'en' for Jeti, the server returns form text in English language. Without the language preference for Jeti, form text is returned in the server's default Czech language (similar to Gajim).