

It is probably due to this change in the Linux kernel. That broke analogue microphone inputs on lots of systems. After that change, there were quite a few additional patches fixing those problems on individual systems (e.g. this one), but there are still lots of broken setups around. I have no idea what the original change was about exactly. It appears to have broken more things than it has fixed, but what do I know.
Yes. Apparently the issue happens with both internal mics and mic connectors where you attach your own mic. The seconds link I provided points to a fix for a specific laptop that fixes a non-working internal mic.