Hi
for anyone following this thread I would summarise as follows:
Setting the access properties of an LO to other and then adding the sites where your LO will be linked should work but you do need to match https to https etc and if your particular platform automatically adds no referrer parameters to the end of the link you may need to manually remove those if you can.
A more reliable way of restricting access is leaving the LO set to private but then using LTI in Xerte and your VLE/LMS so that access is restricted to those who can log in to the course(s) where you add the LTI link and can only be accessed from those courses. There is a brief summary of the Xerte LTI properties in our release notes
xot.xerte.org.uk/play.php?template_id=81#v3.6section4 and a separate guide linked from there on installing Tsugi on your Xerte server so that you can use LTI. Once that's established and you've enabled your Xerte LO for LTI you should then refer to your VLE/LMS documentation as to how to add the LTI link, key and secret.
HTH
Ron