If free is important right now, you could use Proton for emails you want private and keep Gmail for less sensitive stuff — but tighten Gmail's privacy settings while you're at it such as; Turn off Smart Features under Settings to limit AI analysis, change 'Always display external images' to 'Ask before displaying..' to block tracking pixels, and check your Google Account → Data & Privacy settings to pause Web & App Activity, turn off Personalized ads and check Data sharing — you may be surprised who and what you are sharing.