Unionlib adds basically the same mixin as the StructureStartMixin, which uses @Redirect. If only these were injects instead.

any idea's of a fix for this. not familiar enough with that lib to try and make it myself 😢

The situation is quite difficult with no clear path forward. The underlying issue is that both AA and UnionLib add virtually the same mixin, but use the @Redirect mixin type to do so. The thing is, only one such mixin is allowed. For the interested, look here. The mixin is used during world gen to generate an event for all parts of larger structures, such as villlages, nether fortress etc. It's used in AA to map out those structures.

There are a few options here:

1. Change the implementation of the Mixin. I've checked that and I don't see a way to actually achieve that.
2. Just be incompatible. That obviously sucks, but is more or less the status quo.
3. Drop the Mixin. That's not possible at least for AA, as it is needed for village and nether fortress detection.
4. Make AA depend on UnionLib and use its Mixin instead of AA's own one. That is best of all the bad options. However, it means people have to install one more dependencies making it even more complicated to use AA in the first place. People are already overwhelmed with the Architectury mod. So I'm hesitant to go there. Also, while I'm grateful to Stereowalker for the help to keep AA up to date in the past, UnionLib is a very generic helper mod stuffing various things he uses for his mods together. I'd be more inclined to depend on a library mod, which only purpose would be to provide things related to the one Mixin in question aka structure spawning / world gen stuff. And UnionLib isn't that. Also, to my knowledge, no such library exists, yet.

Since all options are bad, I've opted to do nothing about it right now.