Per https://meta.miraheze.org/wiki/Community_noticeboard#YouTube_extension and other users asking, we should probably consider either switching to the original YouTube extension or updating the fork to allow some external sites since some wikis would like to use them.
Per SPF in #miraheze :
SPF|Cloud> Reception123: I recall back then we did not want to support too many external sites for including resources SPF|Cloud> we've never had a discussion about it really, if I'm right SPF|Cloud> but given the fact we support Widgets which are basically unrestricted, and we have the CSP for 'review' now, I'm not against the extension itself