Internationalize custom welcome email

I successfully followed the Nextcloud Portal template ( to customize my welcome e-mails.

However, my attempts to internationalize and translate this customized e-mail have failed. It appears that my customized (extended) EMailTemplate class uses a L10n instance attached to apps/settings, not to my apps/custom_welcome_email.

As a result, my custom internationalization strings, located in a l10n directory within my app, are not loaded. I could manually copy my custom strings into the respective language files of apps/settings, I suppose, but this would be a) tedious; b) prone to break on each NC update; c) overall inelegant.

Any ideas on how to proceed? Basically I am looking for a way to inject a second L10n instance within the overridden EMailTemplate class.

Thank you.