Autism

I'm someone with pretty bad ADHD and with no kids, so take this how you will.

In my opinion, it is still very important to teach your kid about interrupting and how it can bother others. What I'm going to call "interruption culture" between ADHD individuals (at least in my experience) isn't just us interrupting each other whenever we feel like it, but it's a bit of a song and dance.

At least amongst every ADHD person I've met, our speech patterns account for others interruptions (giving a sort of on ramp for the other person to interject, or swiftly continuing to your next sentence so as to say "not yet"), we'll always describe exactly why the interruption is occurring (what train of thought led us to this point, even if it is really roundabout), and is always in a way constructive to the current conversation (if I start talking about Point B after interrupting your Point A, it's because I believe that the two are in some way related and will explain why during my interruption).

The point of the post (in my opinion, I'm not OP) is an indicator that if a person with ADHD interrupts you, it means that they trust and respect you enough to understand why you're interrupting. But that sense of trust and respect comes from the fact that a lot of people do not appreciate interruptions and people with ADHD have to learn to accommodate that. (This is not to say that everyone else should just accept it when an ADHD person interrupts them, but just a fact that people with ADHD don't inherently understand this).

If your child is constantly interrupting, depending on how old they are it might be worth trying to mold the interruptions constructively? Again, I'm not a parent but I was a child with undiagnosed ADHD and can remember what I was like. Maybe it's teaching them that they can't interrupt people mid sentence or mid thought, but intentionally giving them a space to say what they need before returning to their point. Maybe it's getting them to raise their hand before speaking (a sort of "talking stick" approach) to teach them that they need to announce their intent to speak beforehand in some way.

I'm not sure the best methods, but having a constructive outlet definitely helped me as a kid in terms of learning not to just blurt things out. My mother, who similarly to you hates being interrupted, would always stop me if I tried to interrupt once I was in middle school and then tell me when I could start the thought again once she was done. Because of this, I'm pretty good for not interrupting people nowadays (unless they unintentionally use some of the ADHD interruption cues mentioned earlier) and it's definitely made it a lot easier to talk with people because it no longer feels adversarial when talking to me.