Maybe it's too late for an answer or reply but... after you run:
composer require laravel/ui
php artisan ui vue --auth
npm install && npm run dev
This last operation will take several minutes to complete, but at the end it will create the "css/app.css" and "js/app.js" under "public" directory.
This is a sample of output at the end of the operation:
npm WARN deprecated [email protected]: package is bloated with temp files (fixed in 2.3.2)
npm notice created a lockfile as package-lock.json. You should commit this file.
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: [email protected] (node_modules\fsevents):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for [email protected]: wanted {"os":"darwin","arch":"any"} (current: {"os":"win32","arch":"x64"})
added 1008 packages from 486 contributors and audited 17160 packages in 381.48s
found 0 vulnerabilities
@ dev C:\PATH\TO\YOUR\htdocs\laravel-project
npm run development
@ development C:\PATH\TO\YOUR\htdocs\laravel-project
cross-env NODE_ENV=development node_modules/webpack/bin/webpack.js --progress --hide-modules --config=node_modules/laravel-mix/setup/webpack.config.js
98% after emitting SizeLimitsPlugin
DONE Compiled successfully in 17966ms 11:11:37 AM
Asset Size Chunks Chunk Names
*/css/app.css* 173 KiB /js/app [emitted] /js/app
*/js/app.js* 1.38 MiB /js/app [emitted] /js/app