Hello,
Thank you for getting in touch with us.
Rank Math offers a few options for adding before and after your RSS but we do not have the tag you are looking for.
That tag needs to be added inside the post itself if we are not mistaken.
The options offered by Rank Math for RSS are present at WordPress Dashboard > Rank Math > General Settings > Others.
These are the only variables we offer:
Hope that helps and please do not hesitate to let us know if you need our assistance with anything else.
Hello,
Since we did not hear back from you for 15 days, we are assuming that you found the solution. We are closing this support ticket.
If you still need assistance or any other help, please feel free to open a new support ticket, and we will be more than happy to assist.
Thank you.