One of my kids suffered from selective mutism when she was younger. She would speak normally with family, but would not speak outside of the house at all, incl. at school. Not a single word for more than a year.

Creating safe situations where she was forced to speak is the #1 technique to treat that condition. The speech therapists used situations like going out to buy ice cream to get her to speak.

So, yea, think of situations that are comfortable but will force you to speak. It's a very effective technique.

Volunteer to host/speak at a meetup?