Gradine
🏳️⚧️ (she/her) 🇵🇸
Honestly, the biggest logical cause of intergalactic war in a post-scarcity galaxy is the existential threat of pre-emptive annihilation. It is relatively easy, from an aeronautical physics perspective, to fling a big enough object fast enough at any given planet to just wreck everyone's day. Wiping out a potential threat before they do it you becomes an appealing, if also appalling, choice. Doesn't give you a lot of cause for smaller-scale warfare, though.
Beyond that, limiting safe FTL to specific lanes/routes makes control of specific territory significantly more important.
The easiest answer though is not go the post-scarcity route. War often has economic motives, and economics doesn't really play a role without scarcity. Of course, resources could be theoretically (or even practically) possible or even available, but artificially curtailed by those in control of those resources in order to maintain economic and social stratification. Artificial scarcity is one way that elites maintain their profit margins in the face of infinite supply. If you ever wanted to see what this actually looks like in action, try to check out a bestseller as an ebook from your local library.
Beyond that, limiting safe FTL to specific lanes/routes makes control of specific territory significantly more important.
The easiest answer though is not go the post-scarcity route. War often has economic motives, and economics doesn't really play a role without scarcity. Of course, resources could be theoretically (or even practically) possible or even available, but artificially curtailed by those in control of those resources in order to maintain economic and social stratification. Artificial scarcity is one way that elites maintain their profit margins in the face of infinite supply. If you ever wanted to see what this actually looks like in action, try to check out a bestseller as an ebook from your local library.