This post is both to ask for help and to alert potential Mint Mobile customers to the inability (at this time) to record calls both during a phone call and while accessing voicemail in case those people are anticipating being able to use the Mint Mobile line to make a record of a important call.
I have one Pixel 6a with postpaid service with a physical SIM card with a major carrier and another 6a with prepaid service with Mint Mobile with a physical SIM card.
For the postpaid service, recording a call is straight forward either during a call or while accessing voicemail; there are two rows of options
row#1: Mute, Keypad, Speaker
row#2: RTT, Add call, Record call
For Mint Mobile, a Graphene menu option is available to specify both "Audio output format" and "Audio source": [phone symbol] > Settings > Call recording
However, this has no bearing on the inability to record either a call or voicemail.
(1) During a call, the following two rows are present:
row#1: Mute, Keypad, Speaker
row#2: RTT, Add call, Hold
Swiping up in the lower portion, middle portion, or upper portion of the screen does not raise any further menu options. Swiping down offers only the options to hang up or put the call on speaker.
(2) Mint Mobile's method to access voicemail is new to me. After receiving a voicemail, you are presented with icons to play, delete or pause playback of the voicemail. During playback, there is no option present to record the voicemail, and apparently the only offered methods to extract the voicemail are to send the voicemail file in '.amr' format via "Messaging" or "Bluetooth"