Tried with default theme:
Tried with all other plugins disabled:
In old version I could use <i class=”fab fa-youtube”></i> as Title in Arve Link open lightbox but new version seems to require actual text?
My previous test actually did not work correctly. I tested it in a shortcode gutenberg block and obviously you can not use double quotes for the HTML class, but WordPress messes up the quotes of the class I was it transforms single quotes inside the title to double quotes.
I was able to make it work like this inside a shortcode block. Single quotes for title.
[arve url="https://youtu.be/AF2HXId2Xhg?t=26m1s" mode="link-lightbox" title='<i class="fab fa-youtube"></i>' /]
But how WordPress messes with quotes in the shortcode block has nothing to do with the plugin. So that would be the same for 8.0