I really like the idea of having technology hidden from player until they become relevant, as Rubia does by default.
I wanted to have that for more modded planets, which is how I found the "Discovery Tree" mod. Discovery Tree is more flexible in how it hides technologies.
However, Rubia seems to disregard what Discovery Tree does. This leads to "Planet Discovery Rubia" being visible when starting a new game (with all settings default) with both Rubia and Discovery Tree, while all other planet discovery techs are invisible. Most other Rubia techs are listed as question marks, instead of being hidden (which is fine in principle) – while 5 additional techs are fully visible (despite some of their dependencies not being visible?). This is not really a "problem" per se, but it feels very inconsistent to see this behavior.
All other modded planets I have tested seem to be correctly hidden by Discovery Tree. The dev of Discovery Tree mod said this is on Rubia's side and the only way to work around it was to blacklist it. I'd expect Rubia to respect the hiding of technologies performed by Discovery Tree – both mods want to "hide" the techs from the player after all. So it feels like Rubia should not attempt to hide its own techs if Discovery Tree is detected.