I found a partial solution. If I set volume to the lowest when somebody is calling, they barely hear their voice. So my request is that in never version of /e/OS the slider could go even lower. Because now, even when I plug in the external headset, it’s too loud for me to hear when somebody is calling (their voice), and the echo can be mitigated (without headset) by lowering the gain of the caller, so the audio pressure doesn’t influence the microphone. Thanks!
In simple terms, the gain of the caller is set too high by default, and cannot be lowered by slider.
It will take some process to configure / set up your phone again, if you didn’t create usable backups without the “bug” included in them (else they’re unusable).
A factory reset could help to solve bugs and hassle which an update might bring (and some people do a factory reset after bigger updates to ensure a clean configuration to start from), but it is no guarantee. Depending on how much work you’ll have to set up your system again, I would in your situation decide for or against it.
But one aspect is clear: just from resetting the application related data this bug isn’t removed, neither did the recent updates fix it (most probably due to the faulty / misconfigured part not getting overwritten, as no newer version was included).
And without internet access for the applications your phone is quite limited in its functionality…
In your situation I would save / backup whatever is important, do a factory reset, if this doesn’t work, re-flash the /e/ OS via CLI in full process. But this takes its time, needs understanding of the procedure (and the tools ready) and bears risks. For me it still would be better than a phone with such a grave bug.
Edit: Did you maybe set this option? Seems as “Block connections without VPN” option creates flaws for other users which remind me of your symptoms.