Google Meet has the concept of "raising your hand" by clicking a button, which we've used in meetings at work with a fair amount of success. I've also had luck by literally raising my hand on the video (one of the reasons video is actually quite useful for conference calls).
And raising your hand doesn't have to be like when you were in school, it can be as subtle as very slightly raising a finger or 2 (body language).
Zoom has the “raise your hand feature,” and it manages a queue of people who have raised their hands so that they can speak in order. We use this at work, it is especially great for large meetings which otherwise can devolve into chaos.
A small but interesting feature is that each participant can turn on an option where if the software thinks they are physically raising their hand, it behaves as if they clicked the “raise hand” button. I like it.
I don’t use Google Meet, perhaps it has similar functionality.
You’re right, it doesn’t have to be obvious - but if you do it like you did in school, others will usually chuckle and you’ll lighten the mood in the room a bit. I’m a bit of a “funny guy” and so that always works for me, but YMMV of course.
I’d argue conference calls that are audio-only (and thus full duplex, using actual phones) are actually far superior.