Perhaps, but hardware is a gateway to software. The Steam Deck will either be independently profitable, which will give Valve a tonne of additional profit to invest in their store and other hardware (or return to shareholders; this option wouldn't matter so much to GoG), or it will be a loss leader - an effective marketing tool to point people at Steam for gaming. Which in turn provides more profit for Valve. It's generally not good business to do something that drives people towards a product of your competitor, even if it's not a market that you're operating in (unless your end game is to be purchased by them).

I'd also agree that the Linux base would put GoG off - rightly or wrongly, GoG isn't a huge supporter of Linux - and their response to Steam Deck was "You can install Windows on it, and you can play GoG games through Windows".

On VR, I remain to be convinced that it's going to become a viable and mainstream gaming platform, having seen it fail so many times before - but that's probably a different discussion!

yeah, i have always wondered why it got discontinued. i regret not getting one now, it seemed like a decent controller.
you are a little bit late to the party now, as it is viable and mainstream thse days. there are severeal good VR headsets priced from £250-$1000, so iprice is no longer barrier to entry. the headsets have worked out almost all the querks, and VR now works very smoothly. There is now a huge library of vr and vr compatable games, in all genres. the number of headsets and the games are continue to grow year on year, almost exponentially.

so it is now staying, if it was going to fail, it would have done so by now, not continue to grow. today VR gaming is an established market. the critical mass has been reached and passed.

And as an owner of a headset - there are some VR games today that are really good.

That hardware in particular could be a decent gateway to GOG software.

I seriously doubt that GOG supporting SD would drive any measurable profit to Valve. "Oh, I'm going to buy a Steam Deck and start buying Steam games, but only if GOG supports it!" said all of three rather irrational GOG fanboys. On the other hand, if GOG supported Steam Deck, I think there would be more than three relatively normal Steam Deck users who would in the right circumstances be open to checking out the GOG selection of games.

By supporting it, GOG could potentially drive more Steam Deck users towards GOG than they could drive GOG users towards Steam Deck.

Current state of affairs is that GOG is missing out on the entire handheld market; they've got everything to gain. Valve is making bank with or without GOG. Avoiding that market over fear of potentially making a minuscule contribution towards one's competitor's gains could be akin to cutting off one's nose to spite one's face.

I think it's too late though. GOG should've taken Linux support seriously ever since they announced it in.. 2014?

Let me ask this again, what is that people want GOG to support?

I see no point in running Galaxy on top of Steam and most GOG games can be played on the Deck already.
Well, actually the only reason I can think of "GOG support the Deck pls" are cloud saves. Play some game on the Desktop, continue the game while commuting on the Deck and during classes/work on the Laptop.

Either add your native games with 3 clicks, or running non-native thru Proton.

https://boilingsteam.com/valve-breaks-the-shackles-of-proton

I think would be interesting GOG making some kind of bundle with selected games to play on the Deck, eventually with a script to configure them while installing.
Something like older arcade games, historic and/or GOG exclusives. Metal Gear, Re-Volt, Mortal Kombat, Prince of Persia, Metal Slug and a few others.
While interesting I can already ear the outcry why GOG didn't include CyberWitcher Creed xXx and it may hard for GOG to make a selection wich is somewhat neutral in respect to contracts etc (just look how many posts GOG did about Songs of Conquest)