The thing is you can use Let’s Encrypt for private networks too. For example, I use a dns challenge to get a wildcard certificate for a sub domain on my persona

The thing is you can use Let’s Encrypt for private networks too. For example, I use a dns challenge to get a wildcard certificate for a sub domain on my personal site, but those domains only resolve in my house. The wildcard cert isn’t essential for this - you could get individual ones - but it was easier for my home lab.