How to Migrate from Gmail to Proton Mail

I would be a lot more interested in Proton Mail if it had a better way to do compatibility with Thunderbird (i.e., without a local SMTP daemon, and without fees to access this; I am aware of the technical trade-offs in why this solution may be chosen) and had working notifications on degoogled android. Lacking the latter is especially shocking for a privacy-focused company. You can even get working notifications with Gmail on degoogled android via an app like fair email.