laravel/framework v8.9.0 requires php ^7.3 -> your php version (8.0.5) does not satisfy that requirement code example

Example 1: laravel/ui v3.0.0 requires php ^7.3 -> your php version (8.0.2) does not satisfy that requirement.

composer install --ignore-platform-reqs

Example 2: laravel/ui v3.0.0 requires php ^7.3 -> your php version (8.0.2) does not satisfy that requirement.

#It's becouse in your project in composer.json file you have:
"require": {
    "php": "^7.3",
    .....
},

#try this:
"require": {
    "php": "^7.3|^8.0",
    .....
},