self-signed won’t get rid of any warnings, it will just replace “warning this site is insecure” with “warning this site uses a certificate that can’t be validated”, no real improvement. What you need is a cert signed by an actual certificate authority. Two routes for that:

1. Create your own CA. This is free, but a PITA since it means you have to add this CA to every single device you want to be able to access your services. Phones, laptops, desktops, etc.

2. Buy a real domain, and then use it to generate real certs. You have to pay for this option ($10-20/year, so not a lot), but it gets you proper certs that will work on any device. Then you need to set up a reverse proxy (nginx proxy manager was mentioned in another post, that will work), configure it to generate a wildcard cert for your domain using DNS-01 challenge, and then apply that cert to all of your subdomains. Here’s a pretty decent video that walks you through the process: m.youtube.com/watch?v=TBGOJA27m_0