The Error

net::ERR_CERT_AUTHORITY_INVALID at https://my.server.local/files/serve/2afbfeda-35f6-49ec-9f4f-c806829cac17.html

i think its from the cromium-browser on the server, saltcorn use it internal.

http:// works for the Plugin

no plan for add the Cert in the this internal Cromium.