Any Melectronics store will have a large floor-standing cardboard box (marked HP) that will be placed normally near the printer cartridge sales area. If not there, ask as it might be over near the sales desk.
All my "brother" cartridges came with a return box for empty ones. You get a free return shipment label from brother website and just hand it over at any swiss post counter. Maybe you have a similar solution.
Failing that any manned recycling centres will take them.
I took them, last time, to my local ökihof and the very nice operative took them from me. But I wasn't sure if they ended up the compactor or not. Thanks, all!
As mentioned before, larger Migros shops or any larger electronics shop (M-electronics, fust, mediamarkt, etc) should be able to take them. Ask at the customer service desk
I am sure this depends on the commune. I dont know about printer cartridges, but I brought a gas bottle to mine some weeks ago. "Where did you buy this?" "At Manor up the street" "You can recycle it here, but it will cost 20 CHF, if you bring it back to Manor do they have to accept it for free"... so I did.
I was in an Melectronics store yesterday. They have a large box "ökobox" near the cash desk where you can put your toner and ink cartridges. They do not have to be in any type recycle bag.