Idk why this error is occurring, my assumption is the Tiberium mod might of renamed it.

Failed to load mods: PlanetsLib/lib/planet.lua:175: PlanetsLib:update() - planet not found: tiber
stack traceback:
[C]: in function 'error'
PlanetsLib/lib/planet.lua:175: in function 'verify_update_fields'
PlanetsLib/lib/planet.lua:82: in function 'update'
PlanetsLib/api.lua:61: in function 'update'
interstellar-travel/compat/twelpa/Factorio-Tiberium.lua:6: in main chunk
[C]: in function 'require'
interstellar-travel/data-updates.lua:275: in main chunk

Mods to be disabled:
• interstellar-travel (1.0.10)

I am not able to reproduce this issue. Can you please try to provide a minimal list of mods that causes the issue for you?

Factorio 2.0.60
Elevated Rails 2.0.60
Quality 2.0.60
Space Age 2.0.60
Tiberium Dawn 1.012
Factorio Library 0.16.3
Interstellar Travel 1.0.10
PlanetsLib 1.11.1

Can you link the Tiberium Dawn and Factorio Library (nevermind, found this one) mods? I cannot find either of them. Factorio and Conquer: Tiberian Dawn/Factorio-Tiberium is on version 2.0.12 which is completely different than what you provided and seems to be a different mod.

https://mods.factorio.com/mod/Factorio-Tiberium
This is the one i use.

I just realized what you were talking about before, I did typo the Tiberium Dawn version. it's 2.0.12

I am getting the same error when enabling Nauvis has Only Tiberium option, which appears to make Tiber unavailable, causing Interstaller Travel to return this error.

I had this error pop up at first too. This error occurs when the "Factorio and Conquer: Tiberian Dawn" mod is active but does not create the planet Tiber that this mod is looking for in order to relocate it. That only happens if you have changed the settings on Factorio and Conquer. So here is the solution. (edit to add: If you already have a bunch of mods turned on, you can create a new game, save it, do these steps, load the game you saved, sync your mods, exit back to the main menu... you will be back where you started but now you're able to turn on both Factorio and Conquer and Interstellar Journey).

1: Turn off all mods.
2: Turn ON Space Age
3: Confirm (resets game)
4: Go to Settings -> Mod Settings
5: For the "Factorio and Conquer: Tiberian Dawn" mod, change setting "Tiberium Initially Spawns On" back to "New planet Tiber has Tiberium" (this is the default setting so you can just click the reset button).
6: Confirm (resets game)

You can now load the Interstellar Journey (and even the Interstellar Journey Modpack if you wish).