Facing issue "Well, this is embarrassing, we cannot connect to your document. Please try again."

Thanks for that info.

Here are the official Collabora instructions:

Mind following those steps instead?

I did a quick look comparing to the Linode article, and I see Linode had a few different commands. (Perhaps it was based on a slightly older version of COOL?)

Hmmmm… last year, there was someone who had the same exact error message as you.

In March, @switit gave an answer:

That might solve your issue.