I've been updating a FreeBSD jail running on TrueNAS for a few years and never had any issue manually updating the Limesurvey application.  I've just upgraded from 6.1.4 to 6.2.8, and it works fine.

I noticed the jail was running a fairly old version of PHP 7.4.32 so thought I'd update the packages to 8.1.  There isn't a JSON or openssl package as I believe these are now in the core PHP code?  Anyway, all of the other PHP packages were upgraded to 8.1.

When I try and start Limesurvey I now get an error:Internal Server ErrorCall to undefined function Twig\json_encode()An internal error occurred while the Web server was processing your request. Please contact the webmaster to report this problem.Thank you.Any ideas what this might be and how to resolve it?

Thanks