Does Ubuntu work with fast boot turned on? [duplicate]

It depends.

• If you share partitions under Windows and linux, then the option Windows Fast Startup in Windows should be turned off.
• If you do not use any partition that Windows uses under Linux, you can leave Windows Fast Startup in Windows on.

With Windows Fast Startup turned on, as one of its tricks, Windows does not close the partitions it uses. To Linux, these partitions appear "dirty", and linux may either mount them read only or not mount them at all to prevent damage. If you do not use any of these volumes under Linux, that is not an issue, and you can leave Windows Fast Startup on.