I am setting up NextCloud on a PC on my LAN for some friends to use. I have it installed and am now customising it. I want to customise the Welcome email beyond the settings in the Admin screen (colour and logo) such as changing the link from https://localhost/ to the correct URL. To do so I need to change NewUserMailHelper.php or EMailTemplate.php
For example, I have seen other comments on here about changing function addBodyButtonGroup to hardcode the URL to my site.
However, those files are in /snap/nextcloud/28088/htdocs/apps/setings/lib/Mailer and, being a snap installation, cannot be edited.
Is there an alternative solution to this?