Just downloaded and installed the GOTY edition through GOG Downloader.

For whatever reason, the shortcut created on the desktop actually tries to launch the game via Galaxy (or at least the "target" information seems to suggest it).

Does GOG even bother testing the non-Galaxy things anymore? Once I figured it out, it was no big deal to find the executable and remake the shortcut, but damn, if that's the treatment non-Galaxy people get on GOG's flagship title, no wonder things are going down the drain elsewhere.

Also, why does the stand-alone GOG Downloader GOTY version of Witcher 3 suddenly require localhost loopback? I'm getting rather irritated by the number of single-player titles from GOG that outright crash when not given access to 127.0.0.1.

Unfortunately anyone that has GOG games is screwed. I could not even get the GOG downloader to work. Their Galaxy downloader is bundled with an active antivirus so you will be running 2 antivirus programs at the same time which is catastrophic. I shit you not when my computer crashed the bios was affected & I now need a new motherboard. all my events point to GOG galaxy downloader was the problem that forced my motherboard into a compromised situation. My last GOG game I ever buy till they fix this problem. To make it worse on the discussionboards everyone is pissed as hell at GOG for doing this redirect to Galaxy. If your smart never launch from the Galaxy downloader & go into your directory & make an exe. shortcut from there & bypass all of GOG's crap.While I can't fully blame GOG on my motherboard needing to be replaced (as it is 4 years old) It was running a dual boot system fine till I got this game. They just don't have decent enough programmers that know since windows 95 YOU CAN'T RUN 2 ANTIVIRUS PROGRAMS AT THE SAME TIME! And no one is that stupid to disable their antivirus to play their game. They get an F- for stupidity.
No one is responding because their are countless threads running on the GOG downloader problem. If you thought steam was slow downloading this program really takes the cake for 7kbs when my computer can usually whip this out in 17 minutes instead of 3 days.That is using the GOG Galaxy downloader. I am currently trying to get Humble bundle to refund me & just buy the steam version instead or better yet the physical discs since I would rather store & use my backups on my own computer.Cloud does glitch & sometimes you lose all your back up data! Good luck

The OP probably didn't notice and know that the default installers are the galaxy installers. If you want the galaxy free ones, go to the game in your library. Click the More button and choose Classic installers.

The GOG downloader works fine, I'm using it as I type this. Download speed is 10.6 MB/s.
I have Galaxy installed, though I hardly use it. Used it for TW3 to verify my installation. Galaxy didn't come with an antivirus.
Running 2 antivirus programs simultaneously indeed isn't adviced, though don't have to cause a crash. A lot of Windows users actually have 2, if you count Windows Defender. Personally I have BitDefender, Windows Defender and Malwarebytes running. All 3 run fine without any issues whatsoever.
Even if running 2 antivirus crashes Windows, it doesn't cause hardware failure.

You missed where I mentioned I am using GOG Downloader links.

They have always been stand-alone and without bundled Galaxy installation. The installer I downloaded does not actually contain Galaxy, either, but the shortcut it creates it intended for use with Galaxy.

I noticed the downloader comment. A while back I downloaded a game through the downloader and ended up with Galaxy installers. The ones with (g) in the name. Thought you might have had the same experience.

Never had your problem.
My last and current installation of TW3 GOTY is from June 2017. It's 1.31A. No Galaxy stuff in it. Nor did it ever.
Very weird.