That is not really necessary. I believe 99% of the people will just just copy and paste images into composer for most of their needs. ++ select area and + into the composer.
Also copying the image from imgur, or the URL of it works just fine. This report is just a minor corner case.
You can also use Replace a string in all posts to correct all old http imgur links.
Discourse is installed in a Docker container, and we ship updates to nginx so you don’t need support on the host OS. Unless you did a custom setup with a manual reverse proxy, your should have HTTP2 out of the box just by having an up to date Discourse.