Mycroft is a personal assistant similar to siri, alexa, google assistant, or cortana. It is open source. Basically you speak and it does if it has the apropriate extension or skills installed. https://github.com/MycroftAI/mycroft-skills These are not the only skills available and of course more can be created.
We don't really have an alternative per se. You could manually open any application for instance or open your calendar and notate your schedule. You could manually open a timer and set it for what ever time. This essentially can mirror the other personal assistant in function.