Source: Compiled and connected a mouse/keyboard firmware running on an ATtiny861a using internal RC oscillator.
Hell, Atmel even sells Cortex-M chips with High Speed USB-2 support (reasonably hard to find; most are only Full Speed).
I've been doing embedded systems large and small for decades but before this year, never put anything with an ARM into production.
AVRs are still my go to for most things because I know them well and have all the tooling ready to go.
My bad: forgot we were talking 32U4. Here's a link for $2.70: https://www.aliexpress.com/item/32846843498.html?src=google&...
Hell, Atmel even sells Cortex-M chips with High Speed USB-2 support (reasonably hard to find; most are only Full Speed).