Since they are layer 2 applications, you can use anything.
These days, there are wrapped versions of the major coins like Bitcoin so it is easy to integrate into a ETH or BSC smart contract.
We are really getting to the point where the token/coin is actually located is less relevant. The applications will figure out to tie into the proper chains.
Posted Using LeoFinance Beta
Interesting to learn and see developments as they arrive!
Not having managed to keep up with research as I did in earlier years really appreciate your updates!