I have been doing this and it made things worse because I had to open the bag to get more beans out more often. Expelling the air every time should help though. The best method I've seen is vacuum packing single doses of beans but that's a lot of work.

That assumes that a gasket would create a vacuum in the hopper over time. I think fresh air will find a way in anyway. Filling that space with a balloon or a bag is simpler. I will be surprised if this hasn't been done already by a grinder or accessories maker. There are plunger canisters already.

And on the first use of the day, do a one-second grind and discard, to remove the stale grinds from previous day.

Or leave them in for an earthy staleness 🙃

EDIT: Disregard the above, clean your burrs regularly to remove staleness.

That's the principle I had in mind. Applying that to the hopper is the poor man's version and there is no need for further interaction with the beans until you have to refill the hopper. When you open your canister fresh air gets in but I suppose pushing it out seconds later minimises exposure to oxygen. Using a bag and rolling the top before you seal it should achieve the same thing at zero additional cost.

Ah, there is another idea for an entrepreneur. Sealing the bottom between uses. I haven't tested this, but instinctively I think not much air will push its way up compared to the air sucked in from the top as beans drop.

I would think that a plastic bag of rice is anything but porous.

IME storing beans in a foil bag that I open and re-open every day accelerates oxidation even though I roll the top to expel all air. I suppose this is less noticeable if the bag runs out very quickly.