I realise that Google places ads in the native Gmail environment. However, when using a third party front end to embed the Google services, how does the company make money off that? When I use Thunderbird to access Gmail or the Google Calendar or when I map my Google Drive to the file explorer, how can Google profit from this kind of use?
Protonmail (and other proton services) has a Free Tier, and it’s company, Proton AG, were For Profit for a long time (until recently).
Tutanota (now known as Tuta) also has a Free Tier, and is still, to this day, a For Profit company.
Bitwarden allow you to store unlimited passwords, they are a For Profit compant.
Standard Notes let you have Unlimited Notes, and was For Profit until they got bought by Proton
Notesnook also allows Unlimited Notes, and is For Profit.