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You could use mutinynet with that lnd. Just edit the config file to point to that testing network. Then you will need to fork it. The thing is that you will need to simulate or run some various LN nodes on those both chsins.
Mutinynet is a signet though - not sure how I'd fork that. Regtest is open like mainnet/testnet (and it can be just restarted and redone / reproduced for cheap)
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