With my current team lead, 90-minute standups aren't common, but they've happened. 30 minutes is "short", and most take 45 minutes. The previous lead kept things to about 10-15 minutes. The new guy has apparently never in his life said "OK, let's discuss this after standup".
I get why people hate scrum/agile and random standards from above but this is the kind of guy that needs enforcement from his manager. Unfortunately I have never seen that happen and have had to just move on from teams where it gets poisoned like this.
Interject. When things are getting off topic (which is to say, as soon as one person interrupts another person's update with a question) just say "this might be better for post standup", or even just "post standup?" with a questioning inflection.
Most of the people who will mind are exactly the kind of person that you're trying to keep from wasting everyone's time.