howto/yubikey.md

@@ -1165,6 +1165,33 @@ This might happen because GnuPG (or probably a lock contention between
 The fix is unclear, but a workaround is to disconnect and reconnect
 your YubiKey.
 
+### After upgrading to GnuPG 2.4 I can't use my key anymore
+
+If you're running debian sid or you've just upgraded to trixie, you most
+probably switched to version 2.4 of GnuPG. You might then encounter this error:
+
+    # gpg --card-status
+    gpg: selecting card failed: No such device
+    gpg: OpenPGP card not available: No such device
+
+A [NEWS item](https://salsa.debian.org/debian/gnupg2/-/blob/c1b1cb0d4526cb31dea7730d39d8d4945ea837d1/debian/NEWS#L1-8)
+was added to the debian gnupg package to warn about this problem. It used to be
+that gnupg's scdaemon would first try its internal CCID mechanism, fail and then
+default to trying with pcscd and that last part was how we were interacting with
+the yubikeys through GnuPG. The fallback no longer happens, but we can tell
+scdaemon to directly try with pcscd instead.
+
+Open (or create if it doesn't exist) `~/.gnupg/scdaemon.conf` and add the
+following line:
+
+    disable-ccid
+
+Then restart the scdaemon with `systemctl --user restart gpg-agent.service`.
+That should make you able to interact with your yubikey instead.
+
+Note: it's also possible to use CCID *instead* of pcscd, but that change was not
+investigated.
+
 ## Pager playbook
 
 <!-- information about common errors from the monitoring system and -->