I just use different American accents, mostly because I'm American.

Also, because hillbilly gnomes are funny

Undercommon is just really thick Australian accent.

I played a furry porn game where otters spoke Tagalog and honestly, yeah that's fine

Pfft, all dwarves are either Scottish or German. Just a fact.

IMO - Racial/Ethnic/National Coding isn't inherently wrong. But using that coding to push Stereotypes and oppressive mindsets is.

Rule of thumb, if you're worried you will in some way cross that line, don't do coding.

I have my own language mappings in my homebrew. Most of them only appear as names since most people speak Common, but I did include some people in my game who don't. (I make sure that they are some who speak a language that I speak too.) So the mappings are:

1. Common - English. We're playing in English, duh. (Before contact with Elves, humans spoke "proto-Common" which would be mapped to German if I had to use it. Many humans still have German names.)
2. (High) Elvish - French. Yes, in-universe the Common language has plenty of Elvish influence. (Classical Elvish is Latin.)
3. (Wood) Elvish - Greek. Most Wood Elves speak High Elvish, but their names are Greek and many of them still speak their own language as well. The continents and seas are often named in Ancient Wood-Elvish (i.e., classical Greek) because they used to be the primary explorers before the rise of the High Elves.
4. Dwarvish - modern Dwarvish is Norwegian, old Dwarvish is Icelandic.
5. Halfling - Frisian. (Fortunately I haven't had to say anything in Halfling so far.)
6. Gnomish - Welsh. (Again, fortunately I haven't had to say anything in Gnomish yet.)
7. Orc - Russian.
8. Goblin - Mongolian.
9. Tellurian (not a species, but an influential country) - Spanish. Many people alongside the Bay of Luria speak Tellurian as their native language instead of Common or their racial language.
10. Sylvan - Finnish. (My go-to for weirder names as well. Many Fey-related creatures have Finnish names, as well as those who live near Fey portals.)
11. Giant - Hungarian. (They feature a lot in Hungarian folk tales.)
12. Draconic - Hindi.
13. Hashiman (not a species, but a group of eight islands - though they are also the Kenku homeland so most Kenku speak this as their native language) - Japanese-ish. The language comes in two dialects, Hanego which is used primarily by Kenku but also Aaracokra, Owlin, Tortles, and other creatures with hard beaks that have difficulty pronouncing M and N, and Hadago which is used by the rest. They are identical in writing, differ mostly in pronouncing those sounds.

Esperanto is gnomish

Just want to point out that draconic has quite a lot of words already defined, as well as a few grammar rules. 1. Draconic, 2. Draconic Primer, and 3. Lonely Planet Vayemniri (vayemniri being the endonym for dragonborn in the Realms—a race that absolutely despises dragons wouldn’t exactly be happy about a name that says "dragon").

I’m not sure what real-world language would be the best analogue. Maybe something Germanic?

You can't be racist against the French. Same way you can't be racist against dogs.

Latin is Primordial

I use portuguese for common, english for elvish, japanese for abyssal and i'm learning dovahzul to use as draconic, i'm thinking on learning german too but i don't know what it will be yet

Works at larps too. One I go to (in NL) has Dutch as common, and we use English as Elvish and, depending on with whom I talk, I express Dwarvish with either Scottish English, Northern English or German. If I really want to commit to the bit, I should learn High German or an Austrian dialect for Dwarvish.

Jello Apocalypse and crew did a Let's Play of Skies Of Arcadia that was fantastic for a variety of reasons. Everybody in the Chinese-coded nation got Southern accents. It was... an alarmingly apt choice.