I have seen a number of people at #FOSDEM with their laptops out. A small number of them have little covers on their cameras as a sort way of protecting privacy.
None so far have privacy shields on their laptop screens, and anyone sitting beside or behind them had pretty good views of what may have been happening on those screens.
Generic privacy shields are available for about 40€. If your laptop screen has magnets in it (eg MacBooks) then they will attach with those. If not, it’s fairly easy to apply, and they can be taken off at will.
If you travel, or regularly go to conferences or work in public, then please invest in one.