okay first you need to add the new domain to your certificate. You could also just create a new certificate for the new domain only, but to be more flexible, I guess keeping the old domain inside is the better solution for now:
certbot --expand -d old.domain.com,new.domain.com //Replace old.domain.com with the domain/IP you used, to get your first letsencrypt certificate, and new.domain.com with nextcloud-myweb.ddns.net, if I got right.
Source: https://certbot.eff.org/docs/using.html ... rtificates
Then set or add:
ServerName nextcloud-myweb.ddns.net
to the following Apache config files:
/etc/apache2/apache2.conf
/etc/apache2/sites-available/000-default.conf
/etc/apache2/sites-available/000-default-le-ssl.conf
Hmm, I am actually not sure if this is even necessary. You could also skip this first, and see if it works
.The Nextcloud config should be actually still fine, but to be sure, check that within /var/www/nextcloud/config/config.php
you see: 'overwrite.cli.url' => 'https://localhost/nextcloud',
It is possible to set the domain here as well, but since localhost is handled as well, the solution above is the flexible one.