Keep Feather. Block Dawn.

Reinstall Feather 2.6.13-c if needed, then run FeatherClient-Patch before opening the launcher.

Community mirror — not affiliated with Feather, Dawn, or Digital Ingot.

Install-Feather.exe FeatherClient-Patch.zip

Steps

On Dawn? Close Dawn & Feather, run Install-Feather.exe. Still have Feather? Skip this. Patch before opening Feather or it may update again.
Patch. Unzip, double-click Patch Feather.bat, wait for Done. Blocks Dawn updates, removes ads. Backs up originals automatically.
Launch Feather from your desktop shortcut.

Verify the installer

The installer is signed by Digital Ingot, Inc. (Feather's publisher). You can check before running it.

Right-click the file → Properties → Digital Signatures → signer should be Digital Ingot, Inc.
Version: 2.6.13-c · Size: 128,628,624 bytes

SHA-256:

E36573F9990060E72E3083C949BAA444D1BC96A192C58A9F416B7C96A2494BA0

PowerShell — compare with Feather's cached copy on your PC:

Get-AuthenticodeSignature "$env:USERPROFILE\Downloads\Install-Feather.exe"
Get-FileHash "$env:USERPROFILE\Downloads\Install-Feather.exe" -Algorithm SHA256
Get-FileHash "$env:LOCALAPPDATA\feather-updater\installer.exe" -Algorithm SHA256

If the last two hashes match, it's the same file Feather's updater downloaded.

Help

Patch says Feather is not installed: Run the installer first, then patch — don't open Feather until patched.
Antivirus quarantined the launcher: Expected after patching (signature changes). Restore it and run the patch again.
Feather turned into Dawn again: Reinstall, re-patch, then launch.
Undo the patch: Rename .featherfix.bak backups back over the originals in %LOCALAPPDATA%\Programs\feather\.