Developing an email theme that could be used with grapesjsbuilder

Your software
My Mautic version is: 4.02
My PHP version is: 7.4
My Database type and version is: MySQL 8+

Your problem - More of a question … Not a problem
My problem is: - see below -

These errors are showing in the log:

Steps I have tried to fix the problem:

It not a “problem” but a question …

I create an email theme and installed it in my theme management. It got a legacy and email tag on it but i wanted to be able to edit in in grapesjsbuilder.

This is my first theme and I created it with standard html … I assume I need to rebuild the theme using MJML to be able to use grapesjsbuilder editor with it in Mautic?

Bill