The simplest thing you can do is to just use your phone as little as you can.

I use a regular phone because my model doesn't support GrapheneOS or other custom OSs. So I just use my phone as little as possible: calls, whatsapp/LINE/telegram almost only for info about meeting people, not to discuss deep stuff. Proprietary backup deactivated. No games, no superfluous stuff if not a hardened Firefox as browser and my Bank app (sigh). All other few apps I have are FOSS and/or privacy oriented. I use syncthing with encryption enabled so I can backup all data on my desktop with little hassle and regularly delete photos/chats on my phone.

If I have to use a privacy invading app on my phone to buy a parking ticket or something similar: I download the app, block all permissions, use it, delete cache/datas and then delete it.

If I lose my phone tomorrow it would not even be a big deal because I have almost no data in it. I know it's not a perfect model since a few apps and the phone itself do have telemetry, but it's better than going around with a device filled with sensitive data. It reduces a lot of stress and it's very manageable for me.