tymon/jwt-auth 0.5.12 requires illuminate/support ~5.0

for sorry tymon/jwt-auth is not compatible with PHP 8 and to use Laravel 9 you need PHP 8 so, please use lcobucci/jwt instead of tymon/jwt-auth if you want to use Laravel 9 you can install it easily using 

composer require lcobucci/jwt

Note that you might need to upgrade the illuminate/auth to 9 or 8 using 

composer require illuminate/auth:^9.1.0

Good luck