Вот что я получил от Boldbeast Recorder :
Hi,
Android 9 disabled the call recording feature. This is the reason why your own voice is good but the caller's voice is very weak in recordings. No matter what recorder you are using in the market the result is the same. You can test and confirm this fact.
I have checked the Android 9 source code, Google added new limits to block the call recording feature. It is IMPOSSIBLE to bypass the limits without root. So to fix the problem root is the ONLY way to go.
If you root the phone Boldbeast Recorder can fix the problem perfectly, you'll get crystal clear recordings at once. If you don't root the phone there will be no solution in the whole world without doubt unfortunately.
Однако есть и хорошая новость : в телефоне есть своя прога записи разговоров :

Пишет очень хорошо, но необходимо каждый раз вручную запускать.
Круглая красная кнопочка над блутусом - это от болдбиста. Я его отключу, т.к. качество никудышное.