You haven’t asked Grafana to start with TLS/SSL enabled, so it’s not talking HTTPS but regular HTTP (see also the log you attached where the listening address is specified as http://0.0.0.0:3000). Either do that by setting the server.protocol and server.cert_* options or skip TLS entirely by making using http://127.0.0.1:3000 . If it’s just running locally on your computer, not using TLS is fine.
Seeing other posts that reported the same problem via an old, unmaintained-by-grafana package that, incredibly, is out in common circulation and which apparently was either installed by my following the grafana website install installations for debian OR I somehow missed a failure of that installation (unlikely) and wound up using a default that arrived with the latest Raspbian Buster Desktop. ANYWAY, it was as simple as:
This issue usually involves a problem with your web browser or your site’s SSL certificate. The browser’s telling you that because it’s trying to tell you there’s a problem with the certificate the website is using for HTTPS, so “this site can’t provide a secure connection”. In all cases the end-to-end encryption is still going to work just because HTTPS can’t function without it. There is no definite guide for managing this error.
Two possible options to get rid of this issue
Use Self Sign certificate
Remove domain security policy:
Steps for Chrome :
Go to : chrome://net-internals/#hsts
Query HSTS/PKP domain for localhost
Use Delete domain security policies option to delete configuration for localhost