List is not exclusive, of course

JAPAN

Professional organisations:

M-League

JPML

Saikouisen

RMU

NPM

Mahjong Union

Media/news:

Kindai Mahjong

Kinma Web

Mahjong Watch

Mahjong Kingdom

M-League Watch

ABEMA Mahjong

UK

National:

UKMA

European:

EMA (European Mahjong Association)

Clubs:

Leeds https:/leeds.riichi.page/

Guildford https://guildfordmahjong.co.uk/

Bristol https://bristol.riichi.page/

Twickenham https://www.mahjongtwickenham.com/

Waterloo https://www.instagram.com/waterlooriichi/

JKR discord (UK mahjong) https://discord.gg/mXEXCY929v*

USA

National organisations:

American Riichi Association

Professional

Saikouisen USA

World Richi Pro / USPML

Leagues:

American Riichi Mahjong League

Clubs:

Riichi Nomi NYC

Pacific Mahjong League

Philly Mah-Jawn

Seattle Richi

International:

WRC (World Richi Championship)

Mahjong Stars

LEARNING

Beginner

https://mahjong.guide/

YouTube tutorials such as Yu Song's beginner tutorial

Other:

Tile efficiency trainer https://euophrys.itch.io/mahjong-efficiency-trainer

WWYD app, free on both ios and android:search 麻雀一护何

‡J 3 or Ittaku nanikiru