sir_brickalot a privacy friendly dialer app that has "better" multi sim support but still supports recording?
The only dialer capable of recording IS the built in dialer. No other dialer, whether it has recording feature or not, will be able to record. This is because the permissions required for call recording can only be obtained by a SYSTEM application. Installed applications CANNOT obtain the required permission.
As for "GOS won't touch it".... the call recording feature of the built-in dialer is a GOS feature. So my suggestion would be to at least go to github and create a feature request on the dialer, however, the GOS team is pretty small so feature requests are pretty slow to be implemented, if they ever are, so the best thing to do is code the feature yourself and submit a pull request.