Languages Outside the PHB

[Naanomi]

Looking through the Monster Manual I noticed many monsters with languages not in the PHB. Also, I noticed that the Kraken is the only monster that speaks Primordeal directly instead of one of the elemental 'dialects'. Anyways, here is a list in case anyone is interested.

Bullywug, Gith, Gnoll, Grell, Hook Horror, Modron, Otyugh, Sahaugin, Slaad, Sphinx, Thri-Kreen, Troglodyte, Umberhulk, Yeti, Blink Dog, Giant Elk, Giant Eagle, Giant Owl, Winter Wolf, Worg

Note: several beasts on that list, for any ranger taking them as racial enemies

[RedMage125]

Looking through the Monster Manual I noticed many monsters with languages not in the PHB. Also, I noticed that the Kraken is the only monster that speaks Primordeal directly instead of one of the elemental 'dialects'. Anyways, here is a list in case anyone is interested.

Bullywug, Gith, Gnoll, Grell, Hook Horror, Modron, Otyugh, Sahaugin, Slaad, Sphinx, Thri-Kreen, Troglodyte, Umberhulk, Yeti, Blink Dog, Giant Elk, Giant Eagle, Giant Owl, Winter Wolf, Worg

Note: several beasts on that list, for any ranger taking them as racial enemies

Another interesting side issue is that we don't know what alphabet those languages use when written.

Taking a shot at it, I'd say:
Bullywug, Gnoll, Hook Horror, Otyugh, Umberhulk, Yeti, Blink Dog, Giant (any animal), Winter Wolf and Worg do not have written variations. This due to either cultural mores that disdain such things(such as Bullywugs and Gnolls), lack of appendages (animals), or lack of any kind of "society" (Hook Horrors, Otyughs, Umber Hulks).

Gith I would assume uses the same alphabet/written style as Undercommon, since they used to be illithid slaves.

Grell writing would be Brail-like, depending on tactile sense to "read".

Modron would look a lot like Binary.

Sahuagin are extraordinarily intelligent and cultured, so I'm almost sure they have writing. No idea what it would look like though. Maybe hints of Aquan? I'm more inclined to believe that they would have their own alphabet.

Slaad writing would either look like Wingdings, or be comepletely random, and likely no two slaadi would be able to read each others' writing.

Sphinx would probably use symbology from many alphabets, like Primordial and Celestial, and would require a cypher for non-sphinx's to read

Thri-kreen written probably looks like Morse Code, series' of lines and dots.

Troglodyte are basically degenerate lizardfolk in this edition, right? If they write at all, it would probably be very primitive, with hints of draconic, but otherwise mostly crude pictograms.

[Inevitability]

Also, HotDQ has

an intelligent sword that speaks Netherese.

[Rowan Wolf]

Also depending on setting there could be numerous regional languages (mostly of human origin), basically relegating common to a trade tongue not really useful beyond barter/buying/selling and completely lacking areas of vocabulary.

Personally I have been considering a homebrew setting with common as trade tongue and make a few adjustments related to it, i.e. humans speak common, home regional tongue and one additional language of choice.

[Naanomi]

If anyone wants info as to what Ranger Favored Enemy translates into what language choices...

Aberration: Deepspeech, Grell, Otyugh, Slaad, Undercommon
Beast: Giant Eagle, Giant Elk, Giant Owl
Celestial: Celestial, Elvish, Sylvan; +'any'
Construct: Modron
Dragon: Primordial (Aquan), Common, Draconic, Sylvan,
Elemental: Primordial (Aquan, Auran, Ignan, Terran)
Fey: Abyssal, Blink Dog, Common, Draconic, Elvish, Giant, Sylvan, Primordial (Aquan, Base)
Fiend: Abyssal, Common, Gnoll, Infernal, +'All'
Giant: Giant, Orc, Undercommon
Humanoid: VARIES DEPENDANT ON CHOICE
Monstrosity: Abyssal, Celestial, Common, Draconic, Elvish, Goblin, Infernal, Hook Horror, Primordial (Aquan, Base), Sphynx, Sylvan, Umber Hulk, Undercommon, Winter Wolf, Worg, Yeti
Oozes: NONE
Plant: Common, Druidic, Elvish, Sylvan, +'any one language known by it's creator'
Undead: Abyssal, Common, Draconic, Elvish, +'any language known in life', +'five other languages'

INTERESTING NOTES:
*The only Celestial that speaks languages besides 'Any' (Including Celestial!) is the Unicorn
*The only monsters that speak 'Primordial' instead of one of the elemental languages are the Kraken and Night Hat
*The only Plants that speaks languages in the Treant and Awakened Plants
*The only Construct that speaks is the Modron
*Several monsters speak any language, or languages of choice; which may include Druidic (if your Ranger wants to speak it)
*Ooze is the only monster type with no speaking types