Optimum Modpack

Updated:

Architectury (Forge)
Biomes O' Plenty
Caelus API (Forge)
CC: Tweaked
Cyclic
Dank Storage
DeLogger
Dungeon Crawl
Extra Disks
ExtraStorage
Extreme Reactors 2
Extreme sound muffler (Forge)
Forge
ForgeEndertech
FTB Chunks
Item Collectors
LibX
Nature's Aura
ObserverLib
OpenBlocks Elevator
Powah!
Pretty Pipes
Psi
Quark
Shrink.
Simple Storage Network
XNet Gases
ZeroCore 2

Also, You can update The Undergarden mod only before creating a world. If you created a world before updating, you will face a data pack issue which currently doesn't have a solution. If you accidentally updated Undergarden then you can downgrade it to 0.3.8 version to fix this issue.
If you created a world with 0.4.2 version of The Undergarden, you will need to update it each time the modpack updates.
Also, if you created your world with Undergarden 0.3.8 version, updating to 0.4.2 and reverting can result in Nether and End dimensions to disappear. So, take extreme causion and always backup your worlds before updating

There might be an issue where waypoints are not saved between updates. So, you might want to save the coordinates before updating or some other form of saving them like placing waystones to those places.