I remember that in Germany you can buy bags made from corn starch, but they're very thin and very fragile. You need to be really lucky to bring home your shopping bags safely and you definitely cannot reuse them. But you can put them on the compost, which is really cool! If they work on making it a little more robust, bags like that would be my first choice

for some things sure e.g. Italy has had mandatory biodegradable shopping bags for a few years, but for other things, like coke bottles, it seems harder.

I mean, you can enforce glass bottles but that does not seem like a major improvement.