If you are already running the latest Flarum version, you could try adding the -W flag to the commend. This will instruct Composer to update packages that are not listed in the command when trying to find a combination for your environment.
There is a new, different version of diactoros for PHP 8.2, but if you were previously running PHP 8.1 Composer would not automatically attempt to update it when you try installing a Flarum extension.
If you are not already on the latest Flarum, check the Flarum upgrade guide, as otherwise the -W flag could accidentally update Flarum in a way you don't expect.
