Hi @skipper, Backlight 4 is compatible with PHP 8.1 I have applied some silent updates for compatibility, which can be obtained by clicking Reinstall All under Backlight 4 on the Backlight Modules page.
Our policy is to support the latest version of PHP, be it 8.1 or 8.2, with the latest version of Backlight, currently at version 4. That sometimes entails some catch-up as issues come through. I have only had limited time in testing with PHP 8.1 - it was only released three weeks ago and it takes time for our development tools to have the version available for testing. If you do encounter any issues, please let us know and we will endeavour to promptly fix them.