From roasbeef on Twitter: 🚨 attention lnd node operators that have upgraded or are considering upgrading to bitcoind 27 🚨 due to stricter validation for sendrawtransaction added in bitcoind 27 (https://github.com/bitcoin/bitcoin/pull/29434), transaction broadcast will fail if lnd is connected to a bitcoind 27 node:

GitHub

[bug]: sendcoins fails in bitcoind after v27 · Issue #8571 · lightningnetwork/lnd

Background sendcoins fails with bitcoin core version 27. bitcoind before v26.0 lnd sendcoins bcrt1qgy6djk4t4e3l6ldu29r4834zsye2dv9s2h8t5f 1000 succ...

the RPC code in btcd's rpcclient/btcjson library was using sat/KB rather than BTC/KvB (gotta love dem units) for the max fee value, this has been addressed in this PR:

GitHub

btcclient+btcjson: defaultMaxFeeRate to BTC/kvB by YusukeShimizu · Pull Request #2142 · btcsuite/btcd

defaultMaxFeeRate was set to 1e8 / 10(sat/kb) as a parameter. But BTC/kvB is the expected value, so the units was wrong. This updates defaultMaxFee...

we're planning on releasing an lnd v0.17.5 release to address this issue until then, you should hold off on upgrading to bitcoind v27 as transaction broadcast will fail otherwise 🙏