Yes, you can train your chatbot on Notion pages. Just use the Notion integration to connect your Notion account and select the pages you want to train your chatbot on.
From the blog
Custom model training and fine-tuning for GPT-3.5 Turbo
Today OpenAI announced that businesses and developers can now fine-tune GPT-3.5 Turbo using their own data. Find out how you can create a custom tuned model trained on your own data.
Automate your customer support and marketing with Zapier and SiteSpeakAI
With the power of Zapier's 6000+ available apps and integrations, you can now connect your chatbot to your favorite tools and completely automate every aspect of your customer support and brand marketing.