Fatal Error on PHP upgrade

I have inherited a site with a custom theme that was built around 2017. The site works fine in WordPress 7.0 running on PHP 7.4. But, converting to 8.x results in this error: Fatal error: Uncaught TypeError: call_user_func_array(): Argument #1 ($callback) must be a valid callback, non-static method acf_edit_featured_image::init() cannot be called statically …

Quite a few of the line numbers in the stack trace don’t make sense, but I undertand that this is normal.

I also understand from my research that WordPress 8.x is a lot finickier about having functions run with the init hook. So, I’m guessing that is the problem here. Should I start the search by searching for the function call_user_fun_arra() in the theme?

Thanks!