Unlike the MGS1 "fix" this is actually a patch that's installable
Check it out here, it's only 13 MBs: https://github.com/VFansss/mgs2-v-s-fix/wiki

Fitting that a patch would be available, as always "installer beware" due to it being fan software.

Data point of one and all that, but v's fix works very nicely for me with the original pc dvd release on a windows 10 desktop. Widescreen and proper xinput support (triggers!) alone make it worth the effort. It also fixes the notorious 'green screen' bug so you can actually see the video screen in the Tanker. Hopefully it works with the gog release as well.

Can confirm this works perfectly with the GOG version.

I tried it and came back to the original GOG version. It is way better.

*Spit-take* What??? Due to the camera positioning, and your need to actually see what's around you, I'd say this fix is mandatory. Not to mention fixed controller, Dualshock support and 8k downsampling.

Alright, you do you and enjoy your game

Does it allow support for Switch Pro Controllers?

After installing the unofficial patch, are there any remaining known issues with the PC version of the game?
I haven't played MGS2 yet and this sudden port reminded me of that, but I know it's still a really old PC port, and I'm concerned if there's any lingering issues over playing it via other methods

For lots of little reasons the best way to play it is still on an actual PS2, but this version with V's fix is a perfectly acceptable way of playing it.

Sounds pretty good then
I could deal with playing it on PS2 if this port wasn't great, but I really enjoy playing older games at higher resolutions

While V's fix is amazing, it replaces certain files in the GOG version:

1- GOG's dgVoodoo wrapper gets replaced by d3d8to9 wrapper (https://github.com/crosire/d3d8to9/releases). The replaced file is "d3d8.dll". While d3d8to9 is great, dgVoodoo is far more advanced and stable in most games, but testing should be done in MGS 2.

2- GOG's "mgs2_sse.exe" file gets replaced by V's fix "mgs2_sse.exe". It contains certain features such as cheats support, but compatibility wise, it isn't required.

3- V's fix includes Creative ALchemy to make the sound work on Windows 10 and newer sound cards. It isn't required on GOG's release, although I would like to know how GOG implemented the audio fix, because there isn't any trace of ALchemy.

GOG version can work in widescreen and XInput gamepads with these separate fixes:

1- XInput Plus (https://sites.google.com/site/0dd14lab/xinput-plus): This wrapper makes the game recognize the triggers and right stick. I attached my settings to this post.

2- Ultimate ASI Loader's 32-bit version (https://github.com/ThirteenAG/Ultimate-ASI-Loader/releases): Extract it outside the installation folder, rename "dinput8.dll" to "winmm.dll" and place it in the installation's folder "bin" folder.

3- nemesis2000's widescreen fix (http://ps2wide.net/pc.html#mgs2): Create a folder named "scripts" inside the "bin" folder located in the installation folder. Extract all the files from "mgs2.7z" except "d3d8.dll" to this newly created "scripts" folder and rename "mgs2w.dll" to "mgs2w.asi". Then modify "mgs2w.ini" to select the resolution among other interesting fixes (cutscene letterboxing and FOV). Don't forget to change the resolution also in the game's launcher and disable "Motion Blur" (it just looks horrible) and "Focus" (the DOF effect is broken in high resolutions).

Not always a bad thing, gog's d3d8.dll did not work for me, a manual install of dgvoodoo2 did work however and V's fix also worked ontop of fixing some other issues which stock dgvoodoo2 does not address.

originals can be backed up before install if anyone is concerned there. I noticed the sound was excellent and that it seemed to be working with both stock and V's fix, maybe there's a custom audio dll thrown in, diverting EAX calls to openal or software.

I'd recommend disabling Depth of Field which can be done in V's fix settings, and forcing AA/AF etc via your graphics card settings, for me via Radeon drivers, image sharpening works really well with this along with AA and AF looks great.

Which graphical issues does fix v's fix which dgVoodoo doesn't?

dgVoodoo doesn't correct those issues. Depth of Field is not fixed, so it should be disabled, and the FOV fix is included in the widescreen fix, not dgVoodoo.