Same symptoms on Windows 10 Opera 95.0.4635.46 with built-in mic/speakers. Able to send texts and microphone working but no audio during the call. Tried re-installing Opera, disabling extensions, adding voice.google.com to allowed sites etc. but nothing worked until noticing Opera setting called WebRTC set to 'Disable non-proxied UDP'. Changing this setting to 'Use any suitable network interface (recommended)' seemed to fix the problem.
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