If you are searching for FOSS alternatives of basic phone apps like Dialer, Contacts, File Manager, etc. I would recommend you to get Simple Dialer, Contacts, Files,... series of apps. They are both FOSS and minimalist. You can download these apps from F-DROID. If you want to support the developer, here is their donation page:
https://www.simplemobiletools.com/donate/
#FOSS #Android #SimpleApps