> Are there any operating systems that still use cooperative multitasking?

RISC OS uses cooperative multitasking: http://www.riscos.info/index.php/Preemptive_multitasking

There is Wirth and Gutknecht's Oberon System. It's still available but is older than Visopsys -- it was created around 1990, then updated in 2013. I think it's now considered an historical artifact.

https://www.projectoberon.net/

I think it's worth mentioning on a hobby OS, just because it's a decent bit more work to do preemptive multitasking. It's a badge of honor to have successfully implemented it.

Many RTOS support it, eg FreeRTOS’s co-routines: https://www.freertos.org/Documentation/02-Kernel/02-Kernel-f...

> Are there any operating systems that still use cooperative multitasking?

Android ? /s Still not able to run 2 programs in the same time after all these years.