The interview feels like normal work
What you describe for the interview sounds like perfectly normal work situations. I to not think they are actually behaving rude.
I think it is a good thing when the interview process resembles normal work. They probably do not even plan do make it like this, they just continue how they work otherwise.
Being new in a group feels rough
One interesting point:
When entering some social group the first time, very often one has the feeling of the group being rude for a short period.
A good example is starting to ask questions on a new stackexchange site with
a different culture one does not yet understand. I had the case that I asked a question that I was sure is nice - and nobody liked it. Some hours later, I understood that it was perfect for sites I knew - and why it made no sense in the new, different site.
Sometimes you are ignored
It's just realistic that your boss just talks to someone on the phone for minutes, in the middle of a discussion with you. While you are sitting at his desk, feeling ignored.
He may get the work done fastest this way - and may expect you trust his judgement, and see that it may be best in this moment to ignore you. Your job is to accept the situation.
Some members of the meeting may not care what you say - currently
In a meeting in which you discuss some topic with more than one person, it's perfectly normal that part of them is barely listening to what you say - because they are there for discussing specific topics that did not come up yet. Or even to listen to such discussions to learn.
Here, you were discussing the topic whether you fit the job with more than one person, so I don't see any problm when someone is inattentive and using his phone.
Try to see it from their side
I understand that the situation is not polite. But ignoring you for minutes while on the phone in a normal work day in not polite either - they just get the work done, and you do not know which part is most important.
There is ongoing normal work, maybe more urgent than your interview.
I think that most of the rudeness you were feeling was related to different interpretations of the same interview situation.
That could make things look rude that were actually just solutions to technical problems from the other perspective. Or make small active rudeness feel like huge rudeness on your perspective.
But then... maybe it was rude indeed!
Maybe it's all different - we were not there watching the details, and maybe the situation was actually meant as rude, other than what I assumed above.
Just to watch you coping with this slightly difficult situation!
That is a useful idea as you are put out of the formal/cultural rules of the situation. For example, you could get annoyed, bored or angry, and show or surpress that in many ways.
Some of those ways would be more professional, some less.