Are these ripe? The detail that matters with lingonberries
The lingonberries are bright red on the plants, and you describe them as firm but not hard. That combination tells us more than colour alone about whether they are worth picking now.

These are lingonberries, and they look ripe in the photograph. Most are evenly bright red, and you describe them as firm but not hard, which fits lingonberries ready to eat now.
Late August is also a reasonable time for ripe lingonberries in Sweden. I can see a few berries that are still slightly paler red or orange, so for the best flavour straight away, pick the darkest red ones first and leave the rest a little longer.
Pick only healthy, intact berries and rinse them before eating. Next time you check, three things are usually enough to go by: an even red colour, a firm feel and berries that come away easily from the plant.
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