[diogo-plta]

It's right, thank you.

Another useful variable that I can't find is the category or type of the service/product to describe in the invoice.

For example:
{{ line.category }} {{ line.title }} -  {{ line.price}}

Maybe it's not configured. Do you know where these variables used in the email template are configured?

I am testing and preparing fossbilling to work in production, only for invoices and payments, everything indicates that it will be possible.

I appreciate your attention and I hope to follow and help the project.