All this stuff really ignores some real advice that really works.
Anxiety comes from a lack of competence, confidence, or self-awareness. Lack any or all (and we all lack them to some extent) and you’re more nervous.
Get experience talking, presenting, comfort with how you look and sound, practice humor, gauge if you can maintain an audience. These are all practicable things. You can work on them.
I think meditation or mindfulness or any therapy tends to be good for realizing the importance of this, and perhaps some peripheral issues, but would never beat the cause of anxiety because the anxiety is rational. If someone asked me to fly a plane I’d be anxious - and that’s a good response, at a normal level, it means I’d have more cortisol and norepinephrine to react quicker and pay attention. But it’s not great for social things because it makes you shaky, so people see it as more of a fault than a good thing.
A lot of people today want to subscribe to “believe and you can” or “it’s all in your mind” type mantras but to me it’s really backwards to something like, “it’s ok that you can’t, accept it, and with hard work you can.”