The plugin named “Subscribe to Category” in the ClassicPress plugin directory (https://directory.classicpress.net/plugins/subscribe-to-category) has been listed as compatible for CP from version 1.0.0. In testing this plugin I discovered that the plugin is not compatible with CP due to a function call named “wp_set_script_translations()” which was introduced in Wordpress 5.0.0.
I am running a custom theme with the official CP SEO plugin and the official WP Import plugin enabled.
PHP 7.3.27-1~deb10u1 (cli) (built: Feb 13 2021 16:31:40) ( NTS )
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[Wed May 05 13:23:25.785691 2021] [php7:error] [pid 13576] [client 18.104.22.168:51242] PHP Fatal error: Uncaught Error: Call to undefined function wp_set_script_translations() in htdocs/wp-content/plugins/subscribe-to-category/classes/class-stc-subscribe.php:126
If someone could confirm in a test environment we may want to remove that plugin from the directory until the author can push a fix.
WARNING: This plugin WILL make your entire CP website inoperable to please make sure to test on a test CP site.
Update (13:44 EST 05MAY21): I commented out the function in question and there appears to be more incompatibilities with the wpdb->prepare() function which I see has also been updated in WP 5.3.x. Was hoping for a quick fix I could send to the author but no dice on this one.