A V4L2 camera can only be opened by a single application at a time, but if that application is Pipewire, then Pipewire can allow multiple applications to make use of it simultaneously. Same thing with ALSA, it’s the reason sound servers exist at all, though I suspect you’re already familiar with that.
I also hear that ALSA has some support for multiple applications per device nowadays, though I understand it is much less pleasant to use than a fully featured sound server.