Spirit damage replaced alignment damage in Pathfinder 2e since the Remaster.
Unfortunately, no Bestiary came out together with the new Player Core, so it is a bit unclear how spirit damage works. The Player Core says:
Directly affecting the spiritual essence of a creature, spirit damage can damage a target projecting its consciousness or possessing another creature even if the target’s body is elsewhere. The possessed creature isn’t harmed by the blast. Spirit damage doesn’t harm creatures that have no spirit, such as constructs.
So it seems similar to mental, mindless creatures and constructs are immune. Then I found a Reddit, saying about Foundry (I know it is not official, but quite close to it):
Via discord, stwlam has said that they have received clarification and will be updating their rules to allow mindless undead to take spirit damage.
I am happy that mental and spirit do not have the exact same coverage, but it is still unclear for example if Oozes take spirit damage.
Do we have any official or close-to-official list of things immune to spirit damage?