PHP 8.1 issue stops site from functioning

Hi,
I manage a site, http://www.brinckan.se (currently in maintenance mode), and my service provider has forced an upgrade to PHP 8.1.11 which has caused the site to stop working.

WordPress-version 6.0.3
Active theme: INOVADO (version 4.6.6)
PHP-version 8.1.11

E_ERROR detected on line 68 in file:/www/webvol23/9o/7cl2t40n1vnd2l5/brinckan.se/public_html/wp-content/themes/inovado/framework/inc/widgets/custommenu.php.
Reason: Uncaught Error: Call to undefined function create_function() in /www/webvol23/9o/7cl2t40n1vnd2l5/brinckan.se/public_html/wp-content/themes/inovado/framework/inc/widgets/custommenu.php:68
Stack trace:
#0 /www/webvol23/9o/7cl2t40n1vnd2l5/brinckan.se/public_html/wp-content/themes/inovado/functions.php(39): include_once()
#1 /www/webvol23/9o/7cl2t40n1vnd2l5/brinckan.se/public_html/wp-settings.php(566): include(‘/www/webvol23/9…’)
#2 /www/webvol23/9o/7cl2t40n1vnd2l5/brinckan.se/public_html/wp-config.php(120): require_once(‘/www/webvol23/9…’)
#3 /www/webvol23/9o/7cl2t40n1vnd2l5/brinckan.se/public_html/wp-load.php(50): require_once(‘/www/webvol23/9…’)
#4 /www/webvol23/9o/7cl2t40n1vnd2l5/brinckan.se/public_html/wp-login.php(12): require(‘/www/webvol23/9…’)
#5 {main}
thrown

Can you please help me with this?

Kind regards,
Anders

Ticket