Lightbox not working on Discourse

I contacted Linode, they told me to contact Discourse for help.
I contacted Discourse trough this forum, and you guys are recommending me to install the official version.
In this case, we shouldn’t use any marketplace app?

I tried safe mode and that did not help. Isn’t there any way to check what happens with Lightbox and why doesn’t that work? From what I can see, this issue happened for other people, and it was not solved.