tl;dr; Do not remove security manager calls from WildFly or its components! Not unless you want and are able to maintain a branch supporting them for many years.
I don't know all the details, but from a few discussions I've seen in the last hour it seems that the promised removal of runtime support for the Security Manager[1] has landed in an SE 24 update.
This change means in an SE 24 environment you can no longer enable the SM and it will fail if you try. So this will certainly affect our code that's meant to run on SE 24 and later; we'll need to adapt to not try and turn it on.
What this *should not* mean is calls to SM-related APIs in SE will fail. They should still work; they just don't do any enforcement. This isn't some odd situation since for decades now the vast majority of calls to SM APIs don't result in enforcement -- because the user doesn't enable the SM.
WildFly is going to support Java SE versions where the SM works for many many more years. It's only in the upcoming WF 35 that we're dropping support for SE 11. So who knows how much longer we'll need to support SE 21.
If you break SM support in a component, that stream will no longer be usable in typical WF!
We'll need to do things to prepare for the day when SM APIs are removed from SE and we shouldn't ignore that task. But please don't break things.
Kudos to those of you like Richard Opalka and James Perkins who are keeping an eye on things and noticed this promptly.