There’s a very similar discussion thread here: https://www.additudemag.com/forums/topic/concern-for-my-14-year-old-son-and-his-isolation/. You can glean more advice on this in that discussion too.
My daughter, not diagnosed with ADHD but with anxiety, has been much the same all through high school (she just graduated). She tells me she has a hard time reading people and is scared to death of accidentally saying something insensitive, offensive, etc., so she just doesn’t try. She has a few friends but rarely sees them outside of school (they invite her to parties, but she hates parties).
I used to push her to try to do things outside of school with friends. It just stressed her out. Eventually, I accepted that she’s an introvert, has a lot of social anxiety (as do I), and is genuinely more comfortable being at home or with another person one-on-one.
Here’s more on social anxiety:
And on helping teens with social skills:
Continue to address each of your children’s social needs individually.
ADDitude Community Moderator, Author & Mentor on Parenting ADHD, Mom to teen w/ ADHD, LDs, and autism