When visiting Settings > System > Backup > Amazon S3, a 500 error is thrown in the browser. The following is logged to disk:
==> general-alert-2022-04-18.log <==
[2022-04-18T17:53:49.112047+00:00] general.ALERT: Fatal Error (E_COMPILE_ERROR): Array and string offset access syntax with curly braces is no longer supported
{"code":64,"message":"Array and string offset access syntax with curly braces is no longer supported","file":"/home/blestar/public_html/vendors/blesta/amazon-s3-php-class/S3.php","line":2360,"trace":null}
It appears that this vendor code for Amazon S3 is incompatible with PHP 8. Is there a newer version that supports PHP 7.2-8.1+?