Note taking app with collaboration (may be not real time)

Hi guys. I'm looking for note taking app, secure and privacy respectfull, with possibility to share notes between couple of accounts (imagine share grocery list between a couple). It may not be in real time, like when two cursors are shown on screen, but at least with possibility to share notes. Preferably FOSS, of course, but paid options are also good. Can you name some, please?

accounts app collaboration grocery list may privacy real time screen share