I've only just started receiving a response to a refund request filed on the 8th of this month - so others can expect a near 2-week wait if this is any indication.
Unfortunately, GOG have added an extra hoop for purchasers to jump through (in addition to having multiple CAPTCHAs on their support page, auto-cancelling tickets unless you reply to their initial email and pushing you to accept a GOG Wallet refund instead of a real one). You now have to fill in an online form to explain why you want a refund (just in case your initial ticket wasn't clear enough) and this form is *drumroll* a Google form.
So you have to be willing now to supply details via a third party notorious for
large scale tracking of Internet users - GOG has already co-opted its customers via its recent change to its payment system (which now requires users to
permit connections to pay.google.com to use a credit card, whether they use Google pay or not) making this an escalation in its compromise of user privacy.
As it stands, I've posted on the ticket that I will initiate a chargeback on the transaction if the refund isn't given, and will update on how this goes. However others should be aware that the delay in refunds is now only a first step - and the increasing user-hostility that GOG is showing is an increasing disincentive for further purchases.