Justify is not natively supported on BS5, and does not presently work for (at least some, unsure if all) worlds using it. According to someone in #help, apparently a workaround was implemented to fix this, but if it was, it's not working. I attempted to use
Make a BS5 world and attempt to use
Thank you so much for your report! This is not really a bug it is a choice for people with advanced CSS skills to use BS5 therefore they can accomodate this IF they wish.