Fourth generation (8Y, 2020-present) · Premium family hatchback
The current A3 (8Y, 2020-onwards) uses front seats with side-impact airbags in the outer bolsters across every trim. That is the single most important fit factor for a seat cover: it must be explicitly labelled airbag-compatible with a seam engineered to release under deployment force.
Second generation (F3, 2018-present) · Premium compact crossover
The Audi Q3's rear bench slides 150 mm fore and aft and reclines, so a rear cover has to cope with the seat moving. The RS Q3 has sports seats with integrated headrests and very deep bolsters, which universal covers cannot install on cleanly, so that version needs a specialist cover.
Three products we would look at first in this category. Fit for your Audi still comes first: check the compatibility list on the listing against your exact model and year, and read the model guide above.
SakuraSS5370 Heavy-Duty Waterproof Seat Cover Set
Full set with headrest covers; listed as side-airbag compatible on the front covers only.