Although we do not officially support MultiSite, there are clients that have been able to implement. When upgrading to WP 6.3.1 there was this error:
[07-Sep-2023 14:34:20 UTC] PHP Fatal error: Uncaught Error: Call to a member function add_cap() on null in /Users/xxxxxx/Sites/xxxxx/wp-content/plugins/codemonkeys-hipaa-forms/user-role.php:105
Here is the solution: https://dhanendranrajagopal.me/technology/mysql/uncaught-error-call-member-function-add_cap/