Quake lives and it's not going away
How a piece of code send long-lasting tremors all over the gaming world, p. II
After the Quake engine source code was out, it didn't took too long before various ports popped out, but the most interesting were the ones enabling visual features unimaginable back in 1996. Here are some examples…
Tenebrae ex 2002
Among the first was the sourceport from 2002 which showcased 'homegrown' stencil shadows, basically the same tech that Doom 3 would employ two years later. Tenebrae is also memorable by its automatic textures converter that created bump maps (relief) and specular maps (reflectivity) from the original game textures and had water caustics.

Of course, it was rather hungry for computing power: only the powerful system could run it well, besides it'd been often criticized for not being optimized.
The project, however, is long abandoned and even can't be run on Windows 10 systems normally. However, its source code is still out there, although the Sourceforge website isn't quite functional any longer, and houses no screenshots.
There is, however, this flick on Youtube, showcasing the graphics.
Interestingly, the primary developer Charles Hollemeersch got him a stellar career and is now employed by Unity after it has bought out his own startup.
This will take you to places
DarkPlaces is another advanced port - literally a place-to-go for many HD mods for Quake, delivering a lot of formidable features including real-time lighting/shadowing, bloom and support for high-res textures and models and much larger maps. It also supports external music to be played.
It's been developed by LadyHavoc, aka Ashley Rose Hale, who used to work for Google, Meta and now is employed by Mozilla.
DarkPlaces is still in active development, even though it's a long mature and stable port.
There are also a huge 2.7Gb texture Rygel pack and Romi's rtlights (realtime lighting pack) available right at the Darkplaces website.
Besides, there's been also quite a few attempts to make extra games based on the Darkplaces engine, and at least one of them - Doombringer - has made its way to Steam as an early access game.
Dimensions
DarkPlaces, in its own right, has become a progenitor to some other versions, such as Quake 'Epsilon' Build.
It is particularly notable thanks to an HD version of a totally mindblowing Arcane Dimension mod, an 'alternative universe of Quake'. Its original form has a reasonably small size - only 300+ megabytes. The HD version is 2.6 Gbytes; fortunately it's got a standalone version requiring no installers. Only PAK0 and PAK1 files from the original Quake (or its remaster, see below).
Arcane Dimensions per se is primarily a brainchild of a Simon O'Callaghan, aka Sock, a veteran of mapping for Quake-related engines who used to be employed by Splash Damage, Raven Software, Relic Entertainment and even Crytek (where he did some jobs for Crysis game).
His Linkedin states, however, that he's been on Sabbatical for almost 13 years now.
Of course, there were many other contributors to Arcane Dimensions. As they were for yet another crazy HD map pack called 'More Dimensions', this time based on a different source port known as Quakespasm Spiked (aka QSS)... Which is based on Quakespasm... That, in turn, is based on FitzQuake... Jesus, I guess it's high time to stop trying to track all those family ties.
All of these source ports/engines have their own share of sheer awesomeness, capabilities beyond imaginable with the original Quake, enabling modders and artists with new possibilities for self-expression. In the end it is artistry that defines it all.
Tears of False God by Benoit Stordeur, for example, a map of unhealthy vastness and almost blasphemous beauty, has certain vibes of World of Warcraft from the times of The Wrath of Lich King and Cataclysm, with complex - and destructible! - environment.
The architecture is so pretty that you tend to forget about enemies.
Unfortunately they never forget about you. And alas, they are far more than just a nuisance here.
The non-HD version of Tears of False God are included in Arcane Dimension v.1.80. And it can be run on the remastered version of Quake (see below).
HD-version of Arcane Dimension features only the content from v.1.70.
‘More Dimensions’ is a HD compilation of levels which is running on Quakespasm Spiked, and it does include the levels from Arcane Dimensions 1.8 which were not present in 1.7, such as Tears of False God, as well as The Forgotten Sepulcher, which was not present in the HD Epsilon release of Arcane Dimensions 1.7. There are also several third-party Arcane Dimensions levels which are not part of the official release. The latter includes Annihilith of Abhorration, Tomb of Fenrir, The Refinery and "The faults within" (a remake of quake's e3m2 "The Vaults of Zin").
Also stands out FTEQW, one more advanced game engine, a derivative of Quake (or, more exactly, QuakeWorld, the version with improved network code). However, FTEQW is also capable of running Quake2, Quake3, Hexen2, "plus numerous FTE-only mods/games".
It supports a number of renderers, including the very recent Vulkan, OpenGL and DirectX (D3D9, D3D11). The most comprehensive version available for downloads is AfterQuake Package (https://fte.triptohell.info/downloads) that comes with a number of video presets, mods and addons that can be downloaded right in-game.
For instance, that fabulous Rygel's texture pack mentioned above can be downloaded and installed without actually leaving the client. It'll take time, though.
By the way check the version optimized by Matthew Bently which is like 3x smaller.
Besides, it supports real-time lighting and shadows, including what is called 'world lighting' (apparently a sort of Global Illumination implementation). This can seriously affect the visuals, and tax the system, although what is definitely good with FTEQW - it's very fast. Even with Rygel's pack it doesn't start dragging - unlike Darkplaces.
By default it's pretty much colourful and occasionally a little bit overbright, but once you activate real-time world lighting (Options -> Effects) picture changes dramatically. Prepare to fiddle with Gamma/Brightness.
Ah, and by default FTEQW has transparent water (acid is transparent too).
Remaster, with benefits
In 2021 Bethesda and Nightdive Studios, already a household name when it comes to remasters/re-releases of the older games for the modern systems, brought forward the 'enhanced' version of Quake for Microsoft Windows, Nintendo Switch, PlayStation 4, PlayStation 5, Xbox One, and Xbox Series X/S.
It seemingly retained the original, low-res, grittingly pixelated textures, in an obvious attempt to keep faithful to the original game.
However with the remaster came the PC 'port' of Quake 64, originally created by Midway for Nintendo 64 console, as well as Dimension of the Past and Dimension of the Machine. Both had been created by MachineGames, the studio behind 'Wolfenstein: The New Order'.
Dimension of the Past is basically Episode 5 of Quake, semi-officially placed after the events of the original game and before the official expansions Scourge of Armagon and Dissolution of Eternity.
It is more at the classic side, with its brownish palette, sophisticated corridors systems, and enemies coming from every side (making you always regret not having a rear-view mirror).
Originally released in 2016 it also has been given an Epsilon build treatment, making it much more of an eye-candy.

Dimension of the Machine, in turn, is an exemplary exercise in artistry and design prowess: tons of scripted events (such as floors crumbling down when you least expect it), and a far greater feeling of loctaion, 'with more "realistic" landscapes and architecture', as PCGamer noted.
In this regard comparisons to Hexen II come to one's mind (and Heretic II either).
Unfortunately I'm yet to find any mentions of HD version of this particular mod.
As of Quake 64 in the 2021 Quake remaster, it is said to be not an actual port but rather 'a level pack with its level geometry, textures, and soundtrack'.
There is, however, a proper (back)port too.
For the proper wrap-up I've fired up the Quake remaster in order to check whether its multiplayer is still alive.
It is. Not as vigorous as it used to be a couple of years ago, but I had no problem to find a match - and was quickly shotgunned, nailgunned, roughed up with rockets, and got bathed in lava several times.
Quake lives and it's not going away, no matter its age.
Good hunting!