The only functional FOSS call recording app for Android that I'm aware of is the Call Recorder app on F-Droid:
- Call Recorder: https://f-droid.org/en/packages/com.github.axet.callrecorder...
To use this app, you'll need to root your phone using Magisk[1] and the install the Magisk module for Axet's Call Recorder.[2] Then, upgrade the Call Recorder app to the latest version in F-Droid. Note: do not enable "System Mixer Incall Recording" in Call Recorder, since it is not needed and may cause issues with recording.
[1] https://github.com/topjohnwu/Magisk
[2] https://github.com/Magisk-Modules-Repo/callrecorder-axet
The default dialer and contact apps are both FOSS and functional, so I never felt the need to replace them. Signal can take over as the default SMS/MMS app, and there are alternatives with more features such as QKSMS: