I would suggest separating the ideas of speaking confidently in public versus speaking confidently about technology. Specifically I think that the same confidence that can make you an engaging public speaker can be too much confidence for technology conversations.

When it comes to technology I agree with other comments that you should immediately and intentionally set expectations around your level of knowledge on a subject (or conviction about a certain opinion). It's very rare that I can speak so definitively about a subject that it's impossible for me to have biases or gaps in my knowledge. When you speak with a tone of complete authority on a subject you create a game in the room where listening to you is no longer as important as finding a way to pierce the veil of your expertise, which is exactly the situation you would like to avoid. I intentionally say things such as "I could be missing something, but...", "From what I can tell it looks like...", "My personal opinion so far is...", "I'm not saying the other way is wrong, but I can't see how it would be better than...", or "Perhaps the reason I don't agree is that I am misunderstanding something". This language gives me room to have my conclusions, perspectives, and opinions without claiming any dominance or authority over the rest of the room. Being the team expert in a subject is not the same as having perfect intuition or understanding. People will generally understand the difference between doing your best and being perfect, and will gladly accept your best effort as long as you've openly admitted it is not perfect and left room for it to be improved. After all, you're just trying to help reach the best possible outcome. One of my mentors framed this as "It doesn't make anybody look good to kick a friendly dog, so learn from the friendly dog's technique".

The problem is that in order to accommodate these somewhat self deprecating phrases and feel comfortable admitting your imperfect knowledge in public you need to have the confidence to spare, otherwise you'll have an experience similar to overdrawing a checking account. I agree that Toastmasters and debate are two excellent ways to build confidence when speaking with others. I also think that having more one-on-one speaking confidence can translate to public speaking confidence. I always make a point to start conversations with waitstaff, barbers, bartenders, Uber drivers, the person next to me on an airplane, etc. so that I can get small reinforcements that people generally respond positively and at worst are uninterested or indifferent but not mean or aggressive. This helps me keep the mindset that "the worst that can happen is not that bad" when I speak publicly regardless of subject or audience, and one-on-one interactions are much more available than public speaking opportunities.

Conversational experience is also a big tool in maintaining the flow of a presentation, because as you point out unlike a structured debate during meetings people can interrupt you at any time at which point your presentation temporarily becomes a conversation. This is a big reason why memorizing a presentation, reading your slides, and other strictly linear approaches can be inadequate strategies. It is common in conversation to admit that you have never heard of something or don't understand it, and that actually facilitates progress in the conversation. Once somebody explain themselves I am not required to engage further, I can simply say "I'll have to think more, but it's interesting", or "I still don't fully understand, perhaps we could have a longer conversation about this later when I've had a chance to digest what you just told me". I do the exact same thing in meetings, and it is a politely coded way of saying "What you're talking about might be valid but we're going to proceed without addressing it further". You never want to give the impression that there is no room for other people's ideas, just that now is not the right time to expand the scope of this conversation/meeting/presentation. In this way you can maintain control of the overall flow without projecting the authoritarian tone that causes the room to become adversarial.

Lastly always keep in mind that you can be well prepared and demonstrably correct and sometimes you will still be derailed in the moment for silly reasons that have nothing to do with you. I can't seem to find the artist who said this, so maybe I'm paraphrasing the quote, but it's something like "no amount of expertise can prevent an ignorant critique". Try and keep in mind that just as you're not perfect neither is anybody else in the room.