Hello again,

I just wrote a long reply and then I made a wrong move and lost all my text ... So, now, very short:

This is a German tv production by company Intertel Television GmbH (Munich) - the company doesn't exist anymore. It was first broadcast on Swiss tv network DRS (24.9.1978) and later on German tv network ZDF (27.11.1978). Over the years, it was re-broadcast many times; in 2008, many times on special tv channel ZDF Theaterkanal within a few months. More data on the film in German:

https://www.filmportal.de/en/movie/der-kurze-brief-zum-langen-abschied_ea43d4a6e71e5006e03053d50b37753d
https://handkeonline.onb.ac.at/node/2601

EDIT 1

For the first broadcast on ZDF in November 1978 there was a short teaser in the printed German magazine "Der Spiegel" with some more info:

https://www.spiegel.de/spiegel/print/d-40605920.html

"Nachdem Bernhard Wicki wegen Produktionsschwierigkeiten passen mußte, erhielt der Jungfilmer-Veteran Herbert Vesely ("Das Brot der frühen Jahre") den Zuschlag zu dieser Handke-Verfilmung. Bei den Berliner Filmfestspielen 1978 waren die Kritiker befremdet: "Vesely deformierte Handkes Erzählstruktur von Innen- und Außenwelt bis zur Persiflage." Handke selbst fand die schicke und glatte Kinoversion seiner "abenteuerlichen Geschichte", die verschlüsselt in einer Fluchtreise durch die USA die Trennung von seiner Frau reflektiert, durchweg "blöd" und wollte "am liebsten dagegen etwas unternehmen"

Basically, this teaser claims that the film premiered at the Berlin Film Festival in 1978 before shown on tv in November 1978. I can't find any official confirmation online for this at the moment, but the link on filmportal.de above also mentions this premiere at the festival on 28 February 1978. I assume that's correct - and that would be the first screening of the film worldwide. I'm not sure if the film was ever released anywhere else, especially in the UK or the US - I didn't find any info so far.

EDIT 1

There are several copies of this film in different German libraries - but your best shot is the University Zurich:

1.) https://recherche.nebis.ch/primo-explore/fulldisplay?docid=ebi01_prod005357027&context=L&vid=NEBIS&lang=de_DE&search_scope=default_scope&adaptor=Local%20Search%20Engine&tab=default_tab&query=any,contains,der%20kurze%20Brief%20zum%20langen%20abschied&offset=0

You can access the film online when you are a Swiss citizen and live in this country. I did not try this, but here's a description in English how this works:

https://www.zhdk.ch/en/miz/pura-private-user-remote-access-7032

Now you just have to find someone who lives in Switzerland.

2.) https://katalog.uni-konstanz.de/libero/WebOpac.cls?VERSION=2&ACTION=DISPLAY&RSN=1941623&DATA=KON&TOKEN=e3HV9PlfGm3348&Z=1&SET=1

University Konstanz, Germany -> you can rent a DVD with the film on it for 1 week only -> I'm not sure if they ship it to the US (I guess not).

3.) https://katalog.ub.uni-freiburg.de/opac/RDSIndex/Search?lookfor=oclc%3A312826690

University Freiburg, Germany -> you can rent a VHS with the film on it, but only as a member of the university.

4.) https://hds.hebis.de/ubmr/Record/HEB215905334

University Marburg, Germany -> you can watch this VHS with the film on it only in their facility as a member of the university.

These are the places that I found copies of the film for now. Also - I'm not sure if this is of interest to you:

https://handkeonline.onb.ac.at/node/1437

In the last paragraph, it is stated that there is a first draft of a screenplay of this movie in the National Archive of Literature in Marbach, Germany - in the materials of the author of the novel, Peter Handke. In this draft, there's a list of the cast that they wanted to hire - and for Claire Madison, it says "Margarethe von Trotta oder Lea Massari." Which probably means that Alexandra Hay wasn't the first choice for the role she finally played.

EDIT 2

Here's some more information about this first draft of the screenplay. In 1989, film director Bernhard Wicki was asked in a printed interview about the director of this film, Herbert Vesely, and about his own early involvement with it. Here is the online version of the interview in German (the column on the left):

https://www.filmbulletin.ch/full/artikel/1989-10-1_marlon-brando-hatte-auf-mir-als-regisseur-bestanden/

"FILMBULLETIN: War Vesely nicht auch ein grosses Talent? Sein Brot der frühen Jahre zeugte doch von einer grandiosen Virtuosität.

BERNHARD WICKI: Das war mir zu artifiziell-verspielt. Aber ein anderer der Gruppe, Edgar Reitz, hat dafür später mit seiner Fernsehserie HEIMAT ein Meisterstück vollbracht. Vesely hat 1977 einen Film gedreht, den ich eigentlich machen sollte. Das war Der kurze Brief zum langen Abschied, eine Handke-Verfilmung. Den frühen Handke mag ich, den späteren nicht mehr, auch den Filmautor Handke nicht. Der von Handke selbst inszenierte Film Die linkshändige Frau, in dem ich mitgespielt habe, war auch kein guter Film. Aber den Film Der kurze Brief zum langen Abschied hätte ich gerne gemacht und hatte dazu schon Motive in Amerika zusammengesucht. Zu der Zeit, als die lnterTel in Produktion gehen wollte, konnte ich aber nicht, weil ich damals gerade enorme Schwierigkeiten mit Die Eroberung der Zitadelle hatte. Deshalb habe ich das Drehbuch für 200 000 DM an Vesely und die lnterTel abgetreten. Und Vesely hat einen ganz beschissenen Film daraus gemacht. In meiner Kalkulation war der Film unter drei Millionen Mark nicht zu realisieren gewesen. Vesely wollte ihn billiger machen, aber unter ihm ist der Film sogar noch teurer geworden. Mein Buch hat er völlig verändert. Er hat das alles total vergeigt."

Basically, it says that Wicki wrote the first draft of this film, and then sold it to the production company when he left for another project. This most likely means that Alexandra Hay was not considered for a role by Wicki and came on board after he left - the circumstances to be unknown by me. But it seems reasonable that's the reason why she's not mentioned in the first draft.

EDIT 2

I hope that helps! Now I really have to get to my real work...