The parts sellers tend to use the watered down diagrams from Audi USA aka Audi of America (AoA), ie parts.audiusa.com. Sometimes it's good, sometimes it sucks. There's times even when it says part is no longer available when it's in fact the current part revision.
ETKA 8.2 (
https://www.etkainfo.com/home/login) is the actual parts catalog. I assume it's like EPC for MB, a locally installed program that has to be constantly updated. I assume dealerships use this since it's their business, and it limits Internet traffic for every query.
The online ETKA resource is
https://partslink24.com. But I'm not paying $20/month to help you lot out when you post questions. :-P
As such, we owners made due with whatever clone sites we run across.
https://nemigaparts.com/cat_spares/etka/audi/ (was dead, apparently back, still lacks the applicability notes, and still only up through MY17; realoem directs to here)
https://webautocats.com/etka/audi/ (seems a clone of nemiga)
https://audi.7zap.com (recently deceased)
https://7zap.com/en/catalog/cars/Audi/ (but this still works, though I don't like the UI at all)
www.e-acca.com/ (appears to use the same painful page indexing as the "new" 7zap catalog)
www.ilcats.ru/audi/ (good as long as you don't need MY21+).
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