Thanks to the open-source work of jpcima, there's now an easy way for hosts to add support to Reaper's JSFX plug-ins: https://github.com/jpcima/ysfx (package: ysfx-git)
I've already added support in https://ossia.io and it's pretty fun - most likely other DAWs are going to add support over time. This makes me think that it would start to make sense about a standard folder of where to install JSFX effects, a bit like /usr/lib/vst, /usr/lib/lv2, etc. so that the users can install effects through package management (I'll try to add a few free packs that are on github), and all hosts can all scan them automatically.
How about /usr/share/jsfx/<jsfx package>/ ? I'm not sure if share or lib is better for this as those aren't compiled shared objects, but scripts in the JSFX language.
------------------------------ Jean-Michaël Celerier *cto* ossia.io | *consulting inquiries* celtera.dev | *personal* jcelerier.name t: +336 81 31 53 08