In both 1.15 and 1.16, FontManager doesn't implement ResourceReloadListener - it now uses an anonymous class to implement it. However, MixinKeyedResourceReloadListener implements IdentifiableResourceReloadListener on FontManager rather than FontManager$1, so when ResourceManagerHelperImpl.sort traverses the listener list it doesn't find the identifier, making it impossible to declare dependencies on the font resource reload listener.

In fact mojang has in like 1.15 added another default method for displayed name for a resource reload listener. we can probably switch to that