Most people who know me see me as a confident, capable leader. OK, some people see me as an asshat.
Almost no one knows how crippling the anxiety was I felt when I was younger. It still shows itself in one area of my life.
My Dad was a toastmaster. Always exceptional at being in front of the public. That wasn't me (although it is now).
I know what helped me break through it. Scripted opportunities to be in front of other people. For me, this was music and theatre. I wasn't a great musician, but my Dad was a musician. I always wanted to please him, so I played in bands. Jazz bands. Saxophone. Most everyone in a jazz band will take turns taking solos. Often they are improvisational. Sometimes they are pre-written. But there comes a moment when it's your turn to stand up, and play something. I never got to be good enough to improvise well. But I could do the scripted stuff. Stand up, play a few bars, sit down. No words. Made me nervous as crap, but I did it. Made my Dad smile.
Same thing happened with theatre. There are lots of talented outgoing people who like to be center stage. I'm not one of them. But I loved the comradery of the theatre, and played a few small parts. All I had to do was deliver the words someone else had written. It wasn't easy, but I figured it out. Musical theatre was easier. Just deliver the words while singing along.
I didn't realize it when I was young, but those were the training grounds for being a confident outgoing leader. Now, I'm a toastmaster. I'll be a little insulted if you don't ask me to speak. (I still get butterflies, but I enjoy them)
I think this stuff is probably harder with COVID. But I would suggest seeking out the opportunities to force yourself (or your kid) to stand up in front of folks and speak out. Perhaps without words. Perhaps with other people's words. Debate club, poetry slams, singing in a choir, reading to kids, instructing a group for a task... there are many ways to engage (and still plenty in an online world). My son designs scenes and leads Dungeons and Dragons games. OK, not my thing, but it works!
Good luck!