There is no way for a plugin to hook or alter index.html

[JellyHunter]

Hey,

Just wanted to mention, that it is possible.
I do it (copied it myself from Jellyscrub)
https://github.com/Namo2/InPlayerEpisodePreview

The general approach here is that you inject a new script tag into index.html on server start (can fail due to file permissions)
You will bundle a js file with your dll containing every change etc.
The script tag in index.html will call your controller/endpoint which will return the js scipt file from step 2

Sry @SethBacon for disturbing your peacful sleep
and @ devs for any question or problem that will come up because of plugins which do unsupported things

You shouldn't have to say sorry for being creative and finding new ways and ideas to make Jellyfin even better, I salute you bro!