Great question — answering as the UphillTech team:
Not really an answer but too long for a comment: On my most recent trips to Europe I found the immigration experience to be all over the place. Sunday morning two weeks ago in FRA Terminal B the immigration line (containing both EU and non EU citizens) was over 1000 people deep and got routed through some obscure part of the Terminal, just to deal with enormous flood of people that had to stand somewhere. When I departed 10 days later (also FRA), it was a complete non-event. Utterly empty and no lines anywhere. I've had similar experiences at many other European airports over the last couple of years with the worst one probably being LIS which can have atrocious lines that are not only long...
Full answer by Hilmar: https://travel.stackexchange.com/a/204524 (CC BY-SA 4.0).
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