While vkQuake exists already as it's based on Quakespasm but with Vulkan rendering, the Quakespasm Spiked is on entirely different level as it contains lots of new features which both of these source ports lack such as the ability to change the rendering scale with r_scale command, run the game at higher than 72 FPS without causing any issues, expanded limits which makes it more friendly for recent mods (perhaps it should replace vkQuake altogether?). As for Mark V, the source code is sadly offline and besides Darkplaces, this is also a source port which supports mods that require custom engine changes such as Nehahra, should be considered for the legacy use.
Additional information
While vkQuake exists already as it's based on Quakespasm but with Vulkan rendering, the Quakespasm Spiked is on entirely different level as it contains lots of new features which both of these source ports lack such as the ability to change the rendering scale with r_scale command, run the game at higher than 72 FPS without causing any issues, expanded limits which makes it more friendly for recent mods (perhaps it should replace vkQuake altogether?). As for Mark V, the source code is sadly offline and besides Darkplaces, this is also a source port which supports mods that require custom engine changes such as Nehahra, should be considered for the legacy use.