The mail address is not the issue. You can enter any address you want there if you don’t care about Let’s Encrypt being able to reach you in case of problems (they won’t).
Don’t be afraid of the logs. You don’t have to read or understand every line of them. You have an issue with your certificate? Search for certificate and read the lines above and below to get clues what might have gone wrong.
JASN_DE@feddit.org 1 day ago
Selfhosting without checking the logs to hunt down errors? That’s not going to be pretty.