They are missing, which is why every edition that saw fit to publish the encounter distance table as more than GM screen space filler also included concealment rules to extend hard cover from single obstructions to potentially additive visual concealment. Disadvantage in a system that gives players so many was to ignore it even before considering that any single source of advantage cancels out any number of disadvantage.is obviously going to have many ways of making it insufficientMy point in posting that chart is that the "vision range limit rules for the GM" that you seem to be saying are missing have actually been provided. The idea with encounter distance is that there is no awareness of the encountered creature(s) due to intervening terrain, topography, etc. beyond the given rolled distances which average well under the 600' maximum range for a longbow and the maximum of which (in mountainous terrain) is 400'. Chessex does in fact produce a "Mondomat" size battle mat at 54" x 102" which is more than enough space to accommodate the maximum distance in the unlikely event it is rolled.
As for "vision range penalty rules", I'm not sure why disadvantage on the attack roll beyond normal range isn't sufficient, but maybe you have some other kind of penalty in mind.
Almost, obscurement has some problems though. Firstly obscured only hits wisdom perception &doesn't impact attacks like conceal did. It's also worth remembering that any single form of advantage overrides any number of disadvantage sources no matter the number of disadvantaging factors..@tetrasodium Concealment isn't absent from 5e, it's simply known by a different term - Obscured.
Alice helping bob keep watch or bob's familiar helping bob keep watch grants advantage on the disadvantaged perception check imposed by lightly obscured. Even if you do individual perception checks no group of players is going to continue on with one player seeing something the rest can't without taking the time to all see it.
If you use obscured like concealment using "there's a forest between you" lightly obscured gets ignored and heavily obscured imposes blindness which grants...

