One of the positive changes coming to Season 9 is an increased drop rate for Legendary Runes. This includes a flat drop rate increase across the game, as well as an increased drop rate from Lair Bosses and the Kurast Undercity.
Diablo 4 Season 9 Overview Diablo 4 Runes and Runewords Guide
2.3.0 PTR Patch Notes
Runes
The drop chance of Legendary Runes has slightly increased.
Lair Bosses have an additional small chance of dropping a Legendary Rune.
