Ask HN: Alternatives to the Pomodoro technique?

The Pomodoro is the default standard for productivity. It's certainly concise and low-overhead, but can still be scaled into elaborate systems. However, I wonder if anyone ever has problems following it. And if so, what are alternative methods to focused work and productivity?

I've seen only one before- the Flowtime Technique, which is really just Pomodoro with no preset time blocks and with flexible breaks.

https://medium.com/@UrgentPigeon/the-flowtime-technique-7685101bd191