The supplementaries slice maps integration works fine in singleplayer but doesn't seem to work at all on dedicated server.
It is possible to add created slices to the map atlas, but these wont get updated like they do in singleplayer, nor does the Map Atlas create new slice maps on existing slices when necessary.
Furthermore when joining a server for a few minutes only an arbitrary subset of slices in the map atlas are displayed with sometimes maps seemingly shuffled between slices. Like for example a lower slice replacing a map of the top level map until all slices appear in the atlas.

Everytime the selected slice in an atlas is changed, the following errors occure according to the log

[net.neoforged.fml.common.asm.RuntimeDistCleaner/DISTXFORM]: Attempted to load class net/minecraft/client/multiplayer/ClientLevel for invalid dist DEDICATED_SERVER
[net.minecraft.util.thread.BlockableEventLoop/FATAL]: Error executing task on Server
[net.neoforged.neoforge.network.registration.NetworkRegistry/]: Failed to process a synchronized task of the payload: map_atlases:select_slice

Full Stacktrace of one instance of the error

try new version

Seems to work now, thank you.
No more error spam, and the slices maps update and are created now.