Plugin breaks site migration

We were having trouble migrating a client’s site using All In One WP Migration, and the culprit turned out to be this plugin. Here was the stack trace:

Got error 'PHP message: PHP Fatal error: Uncaught Error: Call to undefined function get_user_by() in /public_html/wp-content/plugins/aryo-activity-log/classes/class-aal-api.php:89\nStack trace:\n#0 /public_html/wp-content/plugins/aryo-activity-log/classes/class-aal-api.php(161): AAL_API->insert()\n#1 /public_html/wp-content/plugins/aryo-activity-log/hooks/class-aal-hook-plugins.php(20): aal_insert_log()\n#2 /public_html/wp-content/plugins/aryo-activity-log/hooks/class-aal-hook-plugins.php(26): AAL_Hook_Plugins->_add_log_plugin()\n#3 /public_html/wp-includes/class-wp-hook.php(310): AAL_Hook_Plugins->hooks_deactivated_plugin()\n#4 /public_html/wp-includes/class-wp-hook.php(332): WP_Hook->apply_filters()\n#5 /public_html/wp-incl…', referer:

Deactivating this plugin via FTP fixed the fatal error and allowed All In One WP Migration to finish its migration process.

The error was happening on both PHP 7 and 8.

Is it possible that you’re calling the get_user_by() function in a nonstandard location, such as an early-loaded WordPress hook where it isn’t guaranteed to exist yet? If so, you could probably fix the incompatibility by using function_exists.