Hi there,
the methods provided in that document only apply to Yoast.
Other plugins like RankMath also provide a Function that can be added in that way.
We’re not that familiar with All in One SEO – it looks like they provide a schema breadcrumb which is automatically displayed in SERPS – but not on the front end of the site.
If thats the case then the simplest method of adding Breadcrumbs is this plugin:
https://en-gb.wordpress.org/plugins/breadcrumb-navxt/