Before upgrading from 2.4.24 to 20240729.1, I changed the engine of all the tables to InnoDB (some were already InnoDB). I used PHP 7.3 for the upgrade.

After the upgrade, this error is appearing above the forum content but only up to PHP 7.4.

PHP versions greater 7.4 are only showing errors and no forum content. I need it to work on minimum PHP 8.1, which is what my host is providing.

Before I replaced & updated all the files and folders, immediately after the upgrade, the page was showing 6 errors, which reduced to just 2 (image shared above). I had taken the screenshot and here it is (in 3 parts).