Another way to get over performance fear is go to comedy, especially comedy open mics. They have no song to hide behind and no instrument. It’s about whether they know themselves or not and there’s a lesson in there for people who have fears about performing music on stage or fears about talking into the microphone.
The best are comfortable with who they are. The real thing to practise is being yourself in front of people. One way to do that might be to pretend there’s an audience present when you do the ordinary things you do. Flush the toilet (thank you very much) Boil water for tea (thanks) Burp (thank you, thank you) Empty cat litter (thank you and good night).