You can bring electrical appliances back to any (I think) store that sells similar electrical appliances. It doesn't have to be the actual store you bought it from, just a store that sells similar items. They have to take them.
Examples: The FUST store near me has a container out back in which you can toss in your old electronics. I often brought things to the migros and told them I have 'Electroschrott' - normally, they tell me where to put the items.
By the way... when you buy any electronics, the recycling fee is included in the sales price.
Confirm any similar shop. But most shops discourage it by not having any obvious places to take it. At the Migros and Coop I take it to the customer service counter, at Interdiscount I take stuff to the Cashier.
I think it’s only aesthetics and marketing. Old bulbs, empty printer cartridges, burnt drills and any other broken electrical appliances are not exactly the prettiest sight in a shop that tries to sell this stuff new to people. In shops where aesthetics are not that important (jumbo, obi, hornbach) the boxes for recyclabes are quite visible.
There is a very obvious and prominent place in all and every shop, and have you already mentioned it: The cashiers desk.
As it was said, any shop which sells similar goods must take back your old electronic or electrical stuff no question asked. They cannot refuse it, even if you are not a customer and never will be one.
It’s actually much better to return to a shop. Taking them to the déchetterie means the commune bears the expense of disposal, meaning you pay through your taxes.