How did you switch to dumbphones?

I like the idea of switching to a dumbphone but the issue is that there seems to be no way to still use certains apps I find essential:

- whatsapp for messaging friends
- google maps / apple plans
- booking train tickets
- minute bike renting
- pdf viewer / google drive access for work

Do you have alternatives, workarounds ? Or do you plan everything on a computer and then print it or load it to your phone?