Simplest path is probably to use the old simple mobile tools recorder app on fdroid, which won't be getting any updates. Fossify will likely release their recorder app very shortly, which will essentially be the next update for the smt recorder app.
It is already under active development, they just haven't gotten the first release yet.

Edit:
Another interesting one is DroidRec. It is usually used and seen as a screen recorder, but it has three simple toggles for screen video, device audio, and microphone. If you turn off screen and device audio, it becomes a very nice voice recorder.