@wbuser2022 – you can ignore this bit of the thread and as codejp3 says disable the theme support bit in the plugin and it should work fine
@codejp3 I’ve also been digging at the same time as you !
Presume we are both looking at the free Astra 4.0.2 theme by Brainstorm Force?
If so, this is a traditional WordPress theme, but does have a theme.json file, which is what we are currently using as the acid test for FSE themes. I done some research in the WordPress Developer docs, and ‘normal php’ themes can have this file, but it does affect their ability to use the classic editor.
Astra has this file, but also the normal php files and does not appear to be an FSE theme.
Looking further at the dev docs, the unique thing that an FSE theme must have is a templates directory with an index.html file, which won’t exist on an older php theme.
Unless you have other info, I will shortly change the test to
if ( file_exists( $theme_dir . '/templates/index.html') ) {
....
which should then work better.
Let me know if you agree (or not !!!) ??