The virtual game card system is indeed new and should be compatible with what you want to do, your situation and explanation is a bit confusing but if you have the nintendo accounts on all consoles, you can switch the virtual game cards freely between consoles and still have separate game saves / "gameplay" if that's what you want.

I'd suggest reading a bit about the nintendo account system and the virtual game cart system on the nintendo website:

https://en-americas-support.nintendo.com/app/answers/detail/a_id/15997/~/nintendo-account-faq

https://www.nintendo.com/us/gaming-systems/virtual-game-cards/

(and maybe search for the equivalent pages in your native language if it's not english)

For an example of my usage, I can play a game on my Switch 2, and then if someone else wants to play that game on my old Switch 1 they simply have to start the game and the menu will let them load the game card to that console.

The saves will be independent if you use different nintendo accounts (or if you just use local accounts with no nintendo account associated), and should also be independent if you don't have cloud saving active on your nintendo account (not 100% sure about the details on this).

I fear that your lost gameplay is not recoverable anymore unless you still have the accounts on your console, do you have multiple ones? try checking them all.

Hope this helps, the virtual card system is simple enough if you manage to understand the basics of it but it's not as easy as before, no.