Technology

You can research a phone you like and check if it has an unlockable bootloader, root it, and install something like LineageOS on it. It's fairly straight-forward, not super technically demanding, but it does require some tinkering and time setting up.

xdaforums.com is where the rooting kids hang out, post guides for specific models, upload images et c, you can probably do it in an afternoon with GPT.

The issue is that some apps, notably banking and official type apps, usually don't work as they rely on google services for operation. I solve it by having a cheap secondary phone that I only use for that stuff.

Oh, I almost forgot: FUCK YOU GOOGLE

Is there other alternatives to Apple and Google phones?

There are phones that run on other platforms, but the app library and hardware isn't competitive.

https://en.wikipedia.org/wiki/List_of_open-source_mobile_phones

You could also move most of what you do to a tablet or laptop if you're willing to carry that, and just use the phone as an Internet access device and for phone calls.

EDIT: Or use a cell modem for data and SIP service for phone service and texts, though then you need to have a device that you'll keep on if you want to get incoming calls when they come in. Cell phones are pretty optimized for low idle power usage.