Terry Crews strikes again.
Or is it the other guy I'm thinking of?
'Tis the fellow from the first advertisements;
Other Black Man.
[Animal House 2: The Real Party Animals]
There are also a few oddballs that don't necessarily need Comprehend Languages. Certain more "noble" critters like the Giant Owl, Giant Eagle, and Giant Elk are listed as being able to natively understand Common, Elvish and Sylvan, although they lack the ability to speak these languages.
The less-noble Giant Vulture understands Common, but can't speak it. Curiously, the Elk-Owl-Eagle group all have their
own languages as well, which they can presumably speak with each other (in addition to understanding). Giant Vultures don't seem to feel the need to communicate with one another, and would much rather listen to humans than develop their own language.
Presumably "understands" does not include "is able to read", as I don't imagine there's much literature out in the wilds for them to peruse... As such, you may need to find a tutor to read for them (or teach them to read).
Of course, the INT boosting would be a bit strange here, since all those animals have either 7 or 8 INT. The Giant Ape, meanwhile, has 7 INT but cannot understand any language. Just to make things extra clear.
As for mounted combat, there's a new snag... Apparently there's no clear consensus on how your size and reach are handled when you're mounted. This is difficult when you as a Medium creature occupy a 5'x5' space, while the horse you're sitting on occupies a 10'x10' space. The official response from the devs has apparently been "use your own reach", but no explanation of where you
are when you're using your own reach. Some have interpreted this to mean that you need to use your own movement in order to walk/climb around on top of your mount to the individual spaces that you fit into, but this kinda requires you to homebrew some rules regarding facing.
Curiously, that's also the only way of getting the Charger feat to actually work while being mounted... Since you and your mount technically take two consecutive turns on the same initiative (your choice who goes first), you can't perform the required action sequence (use your action to Dash, traverse 10 feet in a straight line, immediately use your bonus action afterwards) unless you dismount and run the distance yourself. However, if you as a medium or small creature are located on the back of a Huge mount, such as an elephant, the elephant can walk up to an enemy, and then you can take a running charge
along the back of the elephant before colliding with your foe and dealing bonus damage.