All editions agree Umbral Courts are found in the High Umbra
Book of Madness pg. 124 for Umbral Courts gives Western Court, Eastern Court, Egyptian Court. They are related but operate separately. There are rumors of a Lodge of the Sky with primitive gods/beings. See pg. 81 of Blood Treachery added Elemental & Zodiac Courts. Chapter 4 of Book of Madness Revised says all the Umbral Courts are just different ways to see the same, single Umbral Court. Pg. 60 of Mage Storytellers Handbook reinforces this. Pg. 70 Infinite Tapestry adds a Court of Muses. There are 3 groups of Muses: Muses of Media, Muses of Mode & Elder Muses. Mage20 has an infinite number of courts. One for each real-world pantheon or group of gods.
Elemental Courts might be air, earth, fire, water (Western) or earth, fire, metal, water, wood (Eastern) or whatever elements desired. Ideas on pg. 68 Infinite Tapestry.
Western Elemental Court
Eastern Elemental Court