PHP warning after upgrading to WP v6.8

It’s a warning, not an error.

debug.log contains thousands of identical entries:

PHP Notice: Function _load_textdomain_just_in_time was called <strong>incorrectly</strong>. Translation loading for the <code>hbthemes</code> domain was triggered too early. This is usually an indicator for some code in the plugin or theme running too early. Translations should be loaded at the <code>init</code> action or later.

Any idea if it’s the theme itself or one of the plugins that’s responsible?