FixedFloat will forget your transaction after 30 minutes and so if sent way after 30 minutes, my money is sent to the void.
If you enabled RBF when creating the transaction try bumping the fee.
Or try double spending the inputs to cancel the initial transaction.
Will Muun cancelled the pending LN transaction after 24 hours or will it stay like that until on-chain fees are low again? If on-chain fees stay high, will the Muun wallet cancel that pending LN transaction? (I asked because I used a low fee so very certain that on-chain tx will not be mined in 24 hours) If the latter, have my money gone to the void? Need some clarity. Thanks.
There is no 24 hour window for on chain transactions, it takes an average of 2 weeks for majority of nodes to drop a transaction from the mempool.
There is also no void where transactions go, it goes to another address it all depends if you have access to that address.