I’ve been trying for several days and it doesn’t work.
What am I doing wrong?
Your host entries look wrong. And you’ve also got the host/data values reversed.
For example, your CNAME entry should be
app (Name) and
custom.glideapps.com (Data), and should not have your domain name tagged on the end of it.
You should copy/paste the values exactly as they are presented by Glide.