Include a mechanism where a front end user can add an image inline to their page/post/comment/topic/reply and it is uploaded to the media library upon submission.
I’ve not seen any plugin for WP that does this properly.
There’s plenty of plugins allowing front end content submission inclusive images that upload file, and it’ll be in the library after
Basically all form plugins I know have that feature
Some even give you access to the actual media library and add access controls
Many are paid, but for great things you need to pay, that’s just how it is.
Of course most those plugins aren’t cp ready.
But that’s another problem.
Uploading images additionally poses a huge risk for sites specially when possible for non authorized users
If you ever did any research on how image hacks work, you would not be asking for this.
Core isn’t even involved in producing the front end beyond retrieving the post and loading the proper template. Anything that happens on the front end is for plugins to provide.