LagunaLife make sure both your command line PHP version (for Composer) and the webserver PHP version are the same.
The latest version of this extension requires PHP8.0+. Based on your error, you probably are running Composer with PHP8+ but running the webserver as PHP 7.3/7.4.
If able, please share your php flarum info output with us https://docs.flarum.org/troubleshoot
