I had the same issue when I tried them. Use the file explorer somewhere in the dashboard to access the server file system. Inside there is a README. It explains how to set up your own domain. It’s definitely an elest.io issue and not Lemmy.
I have tried elest.io. You get a 7 day (up to $20) trial after adding a credit card.
Setup is easy and you get a running instance in minutes. Setting up custom domain isn’t as straight forward for a managed service though.
The cheapest server costs about $10 per month.
Recommended if you’re looking for a managed solution and don’t wanna bother with setting it up yourself.
Set a language in your profile settings. Should be undetermined at least.