Welcome to the forum @widdop
It can be made to work by disabling reliability and storage efficiency features, and by adding work by you.
https://forum.duplicati.com/search?q=glacier%20order%3Alatest has a bunch of comments on the topic.
The oldest by main Duplicati author is “I would not recommend using Glacier, it is too much of a hassle.”
This details some problems. On the other hand, this reports backup (not restore) “working like a charm”.
What is your goal?