Your phone solution is at best a symbolic gesture, most likely utterly useless, and at worst purchasing an unproven device with unproven security and then using it on T-Mobile that is one of the worst for data security.
The only benefit of the phone is that it doesn't have all the data mining social media apps. If you don't want those, uninstall them from your current phone. You can also turn off location services and revoke all permissions for other apps. The Android source code is publicly available, as is the code for all Android apps. Security flaws are found and immediately called out online.
This whole discussion has a very simple solution: stop using the services that you don't like. Stop using Google search. Stop using any and all social media. Stop using online banking. Stop living in 2022 and revert to 1999 technology.
Or stop worrying because your data is aggregated with billions of other users data. Turn off permissions where you can. Live a normal life. Reduce social media anyway because it's unhealthy and a waste of time. Be happy.