Steps to reproduce:
View any dashboard in the frontend
You will receive a 404 not found for the path assets/styles/vendors/Leaflet/Leaflet/leaflet.css
We expect any files in the vendors folder to be accessible by the frontend.
The following section in /etc/zabbix/nginx.conf is preventing access to the leaflet.css file:
If we remove "|vendor" from the location line and restart NGINX we are able to load the leaflet.css file.
I am assuming that the vendor entry above is supposed to match /usr/share/zabbix/vendor but not /usr/share/zabbix/assets/styles/vendors so the entry will probably need to be updated.