Your LMS publishes your due dates as a private link. Copying it here lets CourseCat show them without ever asking for your LMS password.
Open your LMS and sign in as usual.
Click Calendar in the left-hand menu.
Scroll to the bottom of the panel on the right and click
Calendar Feed.
A box appears with a long link starting
/feeds/calendars/ and ending in .ics.
Copy the whole thing.
Paste it into the Calendar feed box and save.
Keep this link private. Anyone who has it can see your
assignment list, so treat it like a password. It only ever reveals due
dates — it cannot change anything or see your grades.