There will be new compatibility issues, because

1. Lithium renamed its packages to net.caffeinemc.mods.lithium.common Possibly relevant code
2. Lithium will release a neoforge port in the future (No more specific issues known yet)

There are the github actions builds from CaffeineMC/lithium-fabric#566 , releases will be made after some releases that are marked as beta or so.

I have one report of a user mentioning the neighbor table issue, where lithium is accessing the uninitialized neighbor table.

Yes, that is the issue I expected. On Fabric I disable the relevant Lithium mixin, I have added the same on Neo now. Test builds should be available here soon.

Do you expect the Neo version of Fabric to be "fully" released on 1.21.1, or do you think that will only happen in 1.21.2 and above?

I haven't made a decision on that, backports to even older versions may be possible as well.

1. I will adjust the package name, but since the only feature where this is relevant is disabled by default (strange non-reproducible crashes I cannot explain) it is not critical.
2. I will add the necessary code on the NF side of FC. Are there builds for testing available, or do I need to build it myself?

@malte0811 Sorry, I forgot to notify you about the beta release. I see you are already fixing compatibility issues. I can also implement changes on lithium's side to avoid you having to make a new release for 1.21.1 . I guess it means disabling a few lithium settings by default when ferritecore is present

Closing this as #175 and #174 are more detailed.

I've created a new 1.21.1 build with the fix, now waiting for CF to approve it. I usually do not have time for modding during the week, so most things that pop up during the week have to wait until the weekend.