Get the new domain name to replace the old one (e.g. move from yyy.com to zzz.com).

Setup DNA records on the domain provider. Point the hostname to the IP address of virtual server. (e.g. figure below shows the setting for Digital Ocean)

ssh to the virtual server. Setup the new domain, disable HTTPS, remove certs files.

sudo nextcloud.occ config:system:set trusted_domains 1 --value=zzz.com
sudo nextcloud.disable-https
sudo rm -rf /var/snap/nextcloud/current/certs

Install certbot and update certs files.

sudo snap install certbot
cd /var/snap/nextcloud/current
sudo mkdir certs
sudo cp -a /snap/certbot/current/. /var/snap/nextcloud/current/certs/certbot/

Update Let's Encrypt for the new domain.

sudo snap remove certbot
sudo ufw allow 80,443/tcp
sudo nextcloud.enable-https lets-encrypt

Wait until the new domain presents a Nextcloud login page.