It’s used self-signed root certificate. You may replace it by your certificate.
The screenshot you attached is Grafana, not PMM. But none of the two products would be able to ship certificates, because they are issued on the domain name, which is not known ahead of time.
You have two options:
1/ install them as shown in the version above or
2/ use a reverse proxy of your choice (nginx or traefik, for example) to terminate SSL
pmm server - 2.18.0
nginx-controller we r using @atymchuk