Whatever you feel more comfortable with to make it work is fine.
To keep it short, in your case the previous post would resume into either one of these options.
Option 1 (described in the wiki):
yum downgrade nethserver-nextcloud-1.8.4-1.ns7 nextcloud-17.0.2-1.el7
yum update nethserver-nextcloud nextcloud
or Option 2 (untested):
sudo -u apache scl enable rh-php72 -- php -dmemory_limit=512M /usr/share/nextcloud/occ migrations:execute core 17000Date20190514105811
sudo -u apache scl enable rh-php72 -- php -dmemory_limit=512M /usr/share/nextcloud/occ migrations:execute core 18000Date20190920085628
sudo -u apache scl enable rh-php72 -- php -dmemory_limit=512M /usr/share/nextcloud/occ migrations:execute core 18000Date20191014105105