Ursula Broicher (2006, 132) mentions Blumhofer’s reference to Mozart, but seems to have been unaware that it was unknown to the Mozart literature. She also cites a review of the play in the Allgemeine Literaturzeitung (Jena).
According to Broicher, Maximilian Blumhofer was born in Munich on 17 Feb 1759, and died in Aachen on 9 Apr 1835. After finishing school in Munich, Blumhofer, who also apparently trained as a musician, seems to have been active for a few years in St. Petersburg, perhaps with the German Theater there. The title page of Luftschiffer states explicitly that the work was fashioned (“bearbeitet”) for that theater. The title page of another play by Blumhofer, So handelt ein guter Fürst, so handeln rechtschaffene Bürger (Leipzig and Düsseldorf, 1786), carries a similar annotation, and the play is explicitly dedicated to Catherine the Great. However, by the mid 1780s Blumhofer was living in Krefeld, northwest of Düsseldorf. The preface to So handelt ein guter Fürst is dated “Düsseldorf den 24. Nov. 1785” and that of Luftschiffer is dated “Düsseldorf den 21 August 1786.”
Broicher (n. 18) identifies “Freyherr von D . . . .” in “M — — —” as Freiherr Wolfgang Heribert von Dalberg, intendant of the Nationaltheater in Mannheim. Günther von Schwarzburg, composed by Ignaz Holzbauer on a text by Anton Klein, was premiered in Mannheim on 5 Jan 1777. Anton Schweitzer's Rosemunde, on a text by Wieland, was first performed in Mannheim on 20 Jan 1780.
The second anonymous reference is evidently to the theater in Munich. Peter Winter’s Helena und Paris (a work referred to explicitly in Blumhofer’s preface) was written for the Nationaltheater in Munich in 1782, and Blumhofer himself reports that he had an altercation of some kind with Count Joseph Anton von Seeau, the intendant of the Munich theater, after submitting a play. This altercation was serious enough that Blumhofer subsequently received an official judicial warning (Broicher 2006, 131).
In 1780, Mozart had been commissioned by the very same Count Seeau to compose an opera for Munich, the opera which became Idomeneo, first performed on 29 Jan 1781. Thus Blumhofer’s reference to musicians who had “belittled, scorned, and intrigued against” Mozart (“verkleinerten, verachteten und becabalirten”) must refer to musicians in Munich.
Mozart had hoped to parlay his commission for Idomeneo into a permanent position in Munich. Although Mozart’s letters to his father speak repeatedly of his warm reception by the electoral court, and although Idomeneo is generally considered to have been a success, no offer of a position was forthcoming. In a letter to his father on 24 Nov 1780 (Briefe, iv:29, lines 13–118), Mozart refers to “a little cabal” against him, but predicts it will come to nothing: “— wegen <meiner opera> seyen sie ausser Sorg, mein liebster vatter — Ich hoffe das alles ganz gut gehen wird. — <ein kleine Cabale> wird es wohl absetzen — die aber vermutlich sehr Comisch ausfallen wird —. denn — ich habe unter der <Noblesse> die <ansehnlichsten> und <vermöglichsten häuser> — und die <ersten Bey der musick> sind alle für mich [...]”
Blumhofer’s reference to cabals might be regarded merely as hearsay, were it not for the fact that he was born in Munich and went to school there, so he may well have maintained close contacts with the musical community in the city.