Hello,
We provide an LTI 1.3 tool for our customers, and one of our customers uses Totara. They are having problems creating LTI deep links with Safari.
Within a course, they go to add an activity using an external tool. They select the preconfigured tool from the list. If they click the "Select content" button, the select content modal dialog is opened but shows an "invalid request" error. The error originiates from Totara (file: mod/lti/auth.php). This problem only happens in Safari. If they use another browser, it works fine.
This sounds very similar to this Moodle issues (https://tracker.moodle.org/browse/MDL-71887). See also this forum post (https://moodle.org/mod/forum/discuss.php?d=425138). It was fixed quite a while ago, so I'd be surprised if the fix hadn't made its way into Totara's fork. I haven't found any information on how Totara's fork keeps up with Moodle versions to verify this. It may be possible that it has been fixed in Totara, but the customer is using an older version.
If there is a correct channel to report bugs/issues like this, let me know.
Thanks!