Hello! I share with you this method to have Notion.so in your Plus plan totally free.
First go to: https://www.notion.so/product/notion-for-education
Then, register with a .edu email (Emails with .edu.pl ending are not valid).
Finally once registered, in the left panel you will see "Get free educational plan" so just click on it and the plan will be activated.
PROOF:
*PS: This is only the offer, you must search for your educational email on your own*
First go to: https://www.notion.so/product/notion-for-education
Then, register with a .edu email (Emails with .edu.pl ending are not valid).
Finally once registered, in the left panel you will see "Get free educational plan" so just click on it and the plan will be activated.
PROOF:
*PS: This is only the offer, you must search for your educational email on your own*