Privacy on the digno 903kc

I want to buy a SoftBank/Y mobile Kyocera 902 kc/903kc Digno Keitais 3 android flip phone. I’m very new to privacy, but I would like to know if there is anything anybody knows about this phone. Its android ver is 8.1.1 so ( base ), it’s unlocked, it’s a Japanese phone, and I’m able to download apps through apk pure. I just need a phone to make calls, read, listen to music, etc. I don’t want to use it a lot and put a lot of information on it. I was also wondering if it is unlocked and I get mint mobile or t mobile service, how much access to my phone would soft bank or y mobile have? Does it make a difference if it’s unlocked and debloated?

This is the open software, but I don’t really understand it.

It doesn’t have Google play services on it, but it does have pedometer pre installed I believe.