In 2014 the 5.0 Player's Handbook came out, and it included, on page 149, the weapons table. The SRD has I believe the exact same list:
https://media.dndbeyond.com/compendium- ... C_v5.1.pdf
(Page 66 with a one line header on 65 for no good reason)

The only official product to have ever added a weapon is the double-bladed scimitar, exclusive to the Valenar elves in Eberron. Because these guys were created in 3.X, they had a custom exotic weapon, and they did about as good a job as they could porting it in. I bring this up, not because it exists in my game (it doesn't), but because I expected, over that decade that 5.0 was the most current version, for there to be something like an Arms and Equipment Guide that launched a bunch of new weapons - but nope!

With the exception of firearms (which are on a different table) and advanced tech weapons (which by default don't function, but could under some manner of circumstance), weapons that are referred to are always on the table under a different name. This isn't because they are literally the same- a katana isn't the same as a longsword- but because under 5e rules, these weapons will all use the same rules, and someone proficient in one weapon of that class will either be familiar with all, or can quickly become so. Here's a pile of oriental weapons from the DMG page 41:

Battleaxe - fu (China); masakari (Japan)
Club - bian (China); tonfa (Japan)
Dagger - bishou, tamo (China); kozuka, tanto (Japan)
Dart - shuriken (Japan)
Flail - nunchaku (Japan)
Glaive - guandao (China); bisento, naginata (Japan)
Greatclub - tetsubo (Japan)
Greatsword - changdao (China); nodachi (Japan)
Halberd - ji (China); kamayari (Japan)
Handaxe - ono (Japan)
Javelin - mau (China); uchi-ne (Japan)
Lance - umayari (Japan)
Longbow - daikyu (Japan)
Longsword - jian (China); katana (Japan)
Mace - chui (China) ; kanabo (Japan)
Pike - mao (China); nagaeyari (Japan)
Quarterstaff - gun (China); bo (Japan)
Scimitar - liuyedao (China); wakizashi (Japan)
Shortbow - hankyu (Japan)
Shortsword - shuangdao (China)
Sickle - kama (Japan)
Spear - qiang (China); yari (Japan)
Trident - cha (China) ; magariyari (Japan)
War pick - fang (China); kuwa (Japan)

If you looked through there and saw some discrepancies (for instance, nunchaku are explicitly called out as clubs in the monk section of the player's handbook, and the wakizashi is obviously a shortsword and not a scimitar), you're not alone. When I hand out a weapon with a name that isn't in the PHB, you can always ask. If it's not obvious (especially if the chart fucks it up) my intention is to tell you which rules it uses. For instance, if you buy a wakizashi, I'll make clear that this uses the rules for short swords, because this table has it dicked up. Similarly, nunchaku will be treated as clubs because otherwise monks and ninjas wouldn't consider them monk and ninja weapons (I don't think either of those two classes can even use flails).

More relevantly, if you run across weapon types that are specific to certain locations of Nylsanna's stone, I'll let you know what rules they use. If a weapon is pretty alien to your experience you may need to spend some time practicing with it even if you have proficiency with it; if you do, that won't cost any gold or build resources, just the minimum amount of time for a weapon expert to learn the different uses of a close-enough weapon. An example would be the katana we just found; if Dis'Kolandir decided he'd never actually practiced with one (pretty unlikely given he went to Sword and Magic School), he'd need to do so for a little bit before being fluent in it. Similarly, Skattebo could have practiced with one that his tribe had won or inherited, or he could have never seen one before in his life, and if it were the latter case he'd want to practice with it during a few long rests before using it.