i have not had flash installed for at least seven years
here is a screenshot i took of youtube in march 2008, eons before html5 video was a thing, playing via a greasemonkey script that shoved the flv into the vlc browser plugin
we have made rather remarkable progress since then
flash is a lumbering security hole and increasingly obsolete. so help it along. uninstall flash. you can do it!
(ps: you can play twitch, livestream, etc. in a REAL ACTUAL VIDEO PLAYER with this)