Only Linux metrics are captured. MySQL metrics not available in the dashboard

First, those TLS Handshake errors are safe to ignore.

Now you want to confirm you can connect to the exporters correctly, so for example, from PMM Server run a command similar to this:
curl -sk [url]https://192.168.5.203:42002/metrics-hr[/url]

Do you see records? You should on a working system.

Let us know if this works or not, then we can continue troubleshooting