Joinmarket does not exist for mobile devices.

As for coinjoins on Nostr it is called Joinstr and it is very promising as it will be cheaper than Joinmarket.

In Joinmarket if you initiate the coinjoin, you pay all the transaction fees of all the members you decide to put, for example 10 members, and coinjoin transactions are expensive because they use a lot of block space.

In Joinstr the cost is shared among all participants.