No desktop notifications on Windows

[thothi]

We've had a Zulip server running on version 4.6 for a while, but my users told me they are not receiving any desktop notifications on Windows (those popup notifications bottom right Windows generates). After some testing it seemed like this is not a client issue.

I therefore upgraded the Zulip server to 5.2, however the same issue persisted.
Then I went ahead and created a fresh test VM and did a fresh install of 5.2. Sadly the same issue still persisted.
My next step was to install Zulip without docker using the official guide and suddenly desktop notifications started to work.

I still have the docker-zulip server where notifications don't work if you want me to debug anything. Happy to look into this, but I don't see any errors related to this.