There are 2 workarounds possible:
It takes few minutes for most of the transactions to be included in a block. So, you can prepare all the steps in advance and perform within couple of minutes before this transaction is confirmed.
Broadcast transactions with fee rate below 1 sat/vByte
Change Min Transaction Relay Fee in
Either run multiple nodes on testnet with same configuration and add them using
addnode or ignore this step.
Create a transaction with
createrawtransaction, Enable RBF and specify fee rate below 1 sat/vByte with arguments
"replaceable" : true and
"fee_rate" : 0.5 in
Sign the transaction with
Broadcast the transaction with
Check the transaction details using https://chain.so/testnet/btc