The best alternatives to Notion Schedule Manager are Mayday, Calendarist, and Timeblocks. If these 3 options don't work for you, we've listed a few more alternatives below.
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AssemblyAI— The most accurate API for conversational speech-to-text
A free time blocking app that works with Google Calendar. Calendarist gives you a clear picture of your daily life and keeps you on track to reach your goals.