[Samsung Galaxy S10 Questions & Answers] veso266:
well I did it, I have native call recorder on my SIM CSC on my GalaxyS10+ Android 10 now I will tell you how its done

1. Find your cscfeature.xml file (this file hold many thing and also holds the option to enable call recorder

on my Galaxy S10+ Android 10 its in:

where country code is your active CSC (mine is SIM) so my file would be in:

then if you have root copy this file to your computer, its encrypted so you will have to decrypt it for this you will need this program: https://github.com/fei-ke/OmcTextDecoder

you decrypt your file like this: java -jar omc-decoder.jar -i cscfeature.xml -d

it will generate a decrypted file out_cscfeature.xml

then you modify this file and add:

<CscFeature_VoiceCall_ConfigRecording>RecordingAllowed</CscFeature_VoiceCall_ConfigRecording>

your file should look something like mine (it depends what options you have enabled but for SIM CSC it should look like this)

<?xml version="1.0" encoding="UTF-8"?>
<SamsungMobileFeature>
<Version>ED00003</Version>
<Country>SLOVENIA</Country>
<CountryISO>SI</CountryISO>
<SalesCode>SIM</SalesCode>
<FeatureSet>
<CscFeature_Audio_SupportSafeMediaVolumeDialog>TRUE</CscFeature_Audio_SupportSafeMediaVolumeDialog>
<CscFeature_Common_EulaVersion>2</CscFeature_Common_EulaVersion>
<CscFeature_Contact_ConfigImsOpStyle>SIM</CscFeature_Contact_ConfigImsOpStyle>
<CscFeature_GMS_SupportSTSTool>FALSE</CscFeature_GMS_SupportSTSTool>
<CscFeature_Graphics_DisableGameToolsPublicWIFI>TRUE</CscFeature_Graphics_DisableGameToolsPublicWIFI>
<CscFeature_Message_ConfigFreeMessage>off</CscFeature_Message_ConfigFreeMessage>
<CscFeature_Message_EnableReplyAll>TRUE</CscFeature_Message_EnableReplyAll>
<CscFeature_RIL_SupportEsim>FALSE</CscFeature_RIL_SupportEsim>
<CscFeature_Setting_EnableDataRoamingButtonInQuickPanel>TRUE</CscFeature_Setting_EnableDataRoamingButtonInQuickPanel>
<CscFeature_Setting_SupportDefaultScreenMode6500k>TRUE</CscFeature_Setting_SupportDefaultScreenMode6500k>
<CscFeature_SetupWizard_DisablePrivacyPolicyAgreement>TRUE</CscFeature_SetupWizard_DisablePrivacyPolicyAgreement>
<CscFeature_SmartSwitch_ConfigHeadUpNotification>never</CscFeature_SmartSwitch_ConfigHeadUpNotification>
<CscFeature_SyncML_DeleteCpAfterTryingToInstall>TRUE</CscFeature_SyncML_DeleteCpAfterTryingToInstall>
<CscFeature_SyncML_DiscardInvalidNetwpinCp>TRUE</CscFeature_SyncML_DiscardInvalidNetwpinCp>
<CscFeature_SyncML_EnableShowVersionNameAferSuccessfulUpdate>TRUE</CscFeature_SyncML_EnableShowVersionNameAferSuccessfulUpdate>
<CscFeature_SyncML_HideOmcAppDetailPage>TRUE</CscFeature_SyncML_HideOmcAppDetailPage>
<CscFeature_Vision_ConfigBeauty>NLLXX</CscFeature_Vision_ConfigBeauty>
<CscFeature_Vision_ConfigFood>NLLXX</CscFeature_Vision_ConfigFood>
<CscFeature_Vision_ConfigImageSearch>PTRXX</CscFeature_Vision_ConfigImageSearch>
<CscFeature_Vision_ConfigPlace>FSRXX</CscFeature_Vision_ConfigPlace>
<CscFeature_Vision_ConfigPlaceLandmark>SFSGO</CscFeature_Vision_ConfigPlaceLandmark>
<CscFeature_Vision_ConfigPlaceMap>GGLXX</CscFeature_Vision_ConfigPlaceMap>
<CscFeature_Vision_ConfigPlaceWeather>TWCXX</CscFeature_Vision_ConfigPlaceWeather>
<CscFeature_Vision_ConfigShopping>NLLXX</CscFeature_Vision_ConfigShopping>
<CscFeature_Vision_ConfigTextExchangerate>OANXX</CscFeature_Vision_ConfigTextExchangerate>
<CscFeature_Vision_ConfigTextTranslator>GGLXX</CscFeature_Vision_ConfigTextTranslator>
<CscFeature_Vision_ConfigWine>VVNXX</CscFeature_Vision_ConfigWine>
<CscFeature_VoiceCall_ConfigOpStyleForHdIcon>SIM_HD</CscFeature_VoiceCall_ConfigOpStyleForHdIcon>
<CscFeature_VoiceCall_DisableVTOutgoing>TRUE</CscFeature_VoiceCall_DisableVTOutgoing>
<CscFeature_VoiceCall_EnableCallButtonInFdnList>TRUE</CscFeature_VoiceCall_EnableCallButtonInFdnList>
<CscFeature_VoiceCall_SupportVolteCallBarringPassword>TRUE</CscFeature_VoiceCall_SupportVolteCallBarringPassword>
<CscFeature_VoiceCall_ConfigRecording>RecordingAllowed</CscFeature_VoiceCall_ConfigRecording>
<CscFeature_Weather_ConfigCpType>TWC</CscFeature_Weather_ConfigCpType>
<CscFeature_Wifi_ConfigSnsStatus>DEFAULT_ON</CscFeature_Wifi_ConfigSnsStatus>
<CscFeature_Wifi_UseDefaultSecurityAs>WPA2/PSK</CscFeature_Wifi_UseDefaultSecurityAs>
<CscFeature_Wifi_UseRandom4digitCombinationAsSSID>TRUE</CscFeature_Wifi_UseRandom4digitCombinationAsSSID>
</FeatureSet>
</SamsungMobileFeature>

after that, reencrypt the file: java -jar omc-decoder.jar -i out_cscfeature.xml -e

it wil generate: out_out_cscfeature.xml then rename this file back to cscfeature.xml and copy it back to your phone, be sure to set the permisions the same as other files are in the same dir

then reboot and you are done

BTW: I could create HOME_CSC file for everyone to flash with odin, it wouldn't require root and you won't need to perform factory reset, the onlything I don't know is if you flash modified HOME_CSC file does that trip knox? I cannot try that as my knox is alredy tripped but if someone is wiling to root his/her phone and knows it will trip knox than tell me and we can try that, I will provide modified HOME_CSC file and he/she can flash it into his phone and if everything goes well, and knox is not tripped

and here are some more goodies you can put in your cscfeature.xml to get various efects

<!-- Show LTE instead of 4G icon when using Mobile Data -->
<CscFeature_SystemUI_ConfigOverrideDataIcon>LTE</CscFeature_SystemUI_ConfigOverrideDataIcon>

<!-- Show 5G branding -->
<CscFeature_SystemUI_ConfigOpBranding5GIcon>5GAvailable,UseOneShapedIcon</CscFeature_SystemUI_ConfigOpBranding5GIcon>

bonus content (how to update to Android 10 and preserve root): https://www.youtube.com/watch?v=1iwL4i_e8TI&t=1452s