In #635 , you said that the problem is not in CPM, but in a purpur or paper.
I've written to purpur, they said: "Report this to paper."
Then to paper, they said that the problem is in CPM, somewhere there:
https://github.com/tom5454/CustomPlayerModels/blob/0.6.17b/CustomPlayerModels-Bukkit/src/main/java/com/tom/cpm/bukkit/AttributeScaler.java#L26

you can read more detail here: PaperMC/Paper#11015

so here we are here again. Will it be fixed?

To clarify, it shouldn't have broke (it's deprecated for removal), but it did because of poor reimpl. Like @Brokkonaut mentioned in the Paper issue, the plugin should update the code to use NamespacedKeys instead for 1.21.

Hey?

The problem is still there, will there be some kind of patch?