docs: update release notes

Author: hieblmi

docs/release-notes/release-notes-0.21.0.md

@@ -58,8 +58,17 @@
   it becomes available. These methods provide an alternative to the standard
   `MuSig2RegisterNonces` workflow and are only supported in MuSig2 v1.0.0rc2.
 
+* The `EstimateFee` RPC now supports [explicit input
+  selection](https://github.com/lightningnetwork/lnd/pull/10296). Users can
+  specify a list of outpoints to use as transaction inputs via the new
+  `outpoints` field in `EstimateFeeRequest`. The `show_outpoints` field can be
+  set to include the selected outpoints in the `EstimateFeeResponse`.
+
 ## lncli Additions
 
+* The `estimatefee` command now supports the `--utxos` flag to specify explicit
+  inputs for fee estimation.
+
 # Improvements
 ## Functional Updates
 
@@ -122,6 +131,7 @@
 
 * Boris Nagaev
 * Elle Mouton
+* hieblmi
 * Mohamed Awnallah
 * Nishant Bansal
 * Pins