Sorry if it sounds rude, but have you used the web on the desktop in the past 10 years? Anything under 1000px-wide windows and sometimes 1200px-wide ones gets you the “mobile menu” on most websites. It’s a consequence of Bootstrap and other fixed-breakpoint frameworks. Overflow menus like what you see on GitHub repositories are the minority.
Sorry if it sounds rude, but have you used the web on the desktop in the past 10 years? Anything under 1000px-wide windows and sometimes 1200px-wide ones gets you the “mobile menu” on most websites. It’s a consequence of Bootstrap and other fixed-breakpoint frameworks. Overflow menus like what you see on GitHub repositories are the minority.