Out of Milk is one, not sure privacy wise though. there’s an ‘Do Not Sell or Share My Personal Info & Limit Use of My Sensitive Personal Info’ button down, but who knows how much they respect that.
Otherwise, I’ve used it a couple times with my roommate and it works well for listing products and synchronizing between devices. The interface is really simple and it even lets you scan barcodes
What I did for that is I made a second shortcut on my taskbar, so now it lets me open both instances or just one