This question could probably warrant an article-length treatment and I have no relevant expertise, but here are a couple of leads.
The Wikipedia article on the Algerian War has a heading about how the FLN mobilized international support during the period in question. It doesn't mention the Western European left per se, but provides some relevant context. It explains how "the United States had every interest in pushing France to give Algeria its independence," and then continues to describe how the so-called "non-aligned" countries of the Third World movement naturally supported the Algerian cause as well.
As an example, in 1954, a few days after the first insurrection, the
radio in Yugoslavia (Third-Worldist) begun to make propaganda for the
struggle of Algeria. The FLN was invited in 1955 at the Bandung
conference to represent Algeria, which was a huge international
Similarly here is an article which mentions that the Egyptian leader "Nasser was able to negotiate a place for [...] a delegate of Algeria’s FLN to a meeting of African heads of state in Accra in 1958."
My intuition is that there would have been certain currents of the left in Europe itself that also supported the FLN at the time, but I don't know enough to say that for sure. If you are interested in the Italian case, you may want to check out the book Italian Colonialism and Resistances to Empire, 1930–1970 edited by Neelam Srivastava. The introduction quotes Giovanni Pirelli, "an active supporter of the Algerian Front de Libération Nationale (FLN) and a close friend of Frantz Fanon," and then continues:
Pirelli’s understanding of the meaning of the Italian Resistance was
shaped by his subsequent involvement with the Algerian cause. Later
chapters of this book explore the extraordinary influence Third-World
revolution had on Italian radical culture of the postwar period,
tracing its effects in the “resistance aesthetics” of films such as
Gillo Pontecorvo’s The Battle of Algiers (1966) [...] It is important
to remember, however, that the relationship the postwar Italian left
had with anti-colonialism was contradictory and ambivalent, to say the
least: on the one hand, there was great support for anti-imperialist
struggles such as those in Algeria and Vietnam, and, on the other, a
puzzling amnesia in relationship to Italy’s own colonial past.
The Battle of Algiers was clearly influential for the international left well beyond Italy, although I'm not sure how indicative that is in terms of how the Cafe War was seen and discussed at the time itself as you are asking.