I have a failed mod load error:
"Failed to load mods: Error in assignID: item with name 'ei-imersite-quantum-age-tech' does not exist.
Source: rubia-unknown-technology-rubia-biofusion-promethium-science-pack (technology).
Mods to be disabled:
rubia (0.69.95)
exotic-space-industries (1.8.0)

It sounds to me like exotic space industries is automatically adding an invalid item to a Rubia technology that isn’t even supposed to have any item costs.

Please bring this to the developer of exotic space industries.

Good news and bad news.

Good news: I figured out the problem. ESI changes the science costs for everything in the game to use its own science packs. ESI automatically added its own science costs to this “rubia-unknown-technology-….”, which is supposed to be a trigger technology (no science costs anyway!). This “quantum” science pack is added to the tech cost, and later ESI (or other mod?) deletes the science pack from existence, which causes factorio to crash.

The reason I am not seeing the same crash is mostly likely because you have a different mod that is either messing with the technologies or mod load order, leading to a different result from me. The offending mod is likely an optional dependency of ESI or Rubia.

Bad news: This is almost certainly ESI’s fault for going up to one of my trigger technologies and adding a science cost for a non-existent science pack. I can’t do anything to help you with this. You need to contact the dev pf exotic space industries to request he fix his mod. You probably want to link this post to bring him up to speed. I’ll be marking this post as resolved, as my work here is done.

After updating rubia, the game won't load.

I would need more information than that. I recently fixed an issue with shattered planet + muluna updates. Please check if the new 0.69.97 fixes your problem.