You might already know about Underscores, often abbreviated as _s, which is a popular starter theme for WordPress. This is a big project maintained by
Understrap - WordPress theme
60 Best Responsive WordPress Themes (Free and Paid) - Hongkiat
60 Best Responsive WordPress Themes (Free and Paid) - Hongkiat
A walk-through tutorial on using Create Block Theme plugin
How to Create a WordPress Child Theme with underscores starter
60 Best Responsive WordPress Themes (Free and Paid) - Hongkiat
Underscores.me — The Best Way To Get Started With The _s Theme
Create A WordPress Theme From HTML Part I - Web Courses Bangkok
Learn to Build Custom WordPress Themes with the Underscores (_S