Trying to install 2 smart switches but neutral wires in box are not connected
Some locations (switches) may have a neutral, others may not. Depends on the previous electrical installations, electrician/installator...with smart switches is exactly the same, depends on the model of the smart switch. Some need that neutral wire, others not. But the vast majority of smart switches require that neutral wire.  I'd connect the dining room neutral wire to the smart switch (let's just say A) and then other 2 together under one cap plus a white wire which goes to the other smart switch B. Remember all the neutral wires that are connected should belong to a single circuit.