It's been some time since I (cyberpwn) have touched Iris, Here's a set of changes from the community, myself included.

• Fixed a lot of issues with downloading packs & loading into worlds. Looks like there were some issues reading the listing
• Fixed an issue that caused Iris to micro-stroke whenever it saw the new biome type "CUSTOM" (1.16.5+). This is sadly an NMS fix so newer versions will have to wait for direct support before the bug is fixed for those future versions.
• Removed a debugging log about a player's location when seeing some effect. I'm guessing it's from someone debugging in the past.
• Fixed a lot of issues with wands, spawns & effects
• EnginePlayer now runs async (effects wont hit your tickrate.. it wasnt using more than 1% but now it's async)
• Bandaid patch to fix villagers from despawning
• If you're a dev in Iris or contribute to it at all, Iris is now using Gradle (i'd consider that a fix at this point)