After installing Sublime Text on Windows 10, I can not change the default application for files with the .txt extension anymore.

Right-clicking on Context Menu > Open With… > Choose Default Program, I can select Sublime in the dialog and check "Always use this application." The file is opened once with the chosen application, but the default remains as the Windows Editor.

In the Windows Settings, I am also able to select Sublime in the dialog for .txt files, but the file type remains assigned to the Editor.

Things that did not help:

• Restarting


• Checking the registry key in HKEY_CLASSES_ROOTApplicationssublime_textshellopencommand
  


• Uninstalling Sublime Text

Using ftype worked, but is unwieldy.

What exactly could have broken the standard file type association dialog? Is it repairable?

Unfortunately, this is a known issue caused by a recent Windows update, and it is tentatively scheduled to be fixed later this month:

Symptom

After installing this update, some users cannot set Win32 program defaults for certain app and file type combinations
using the Open with… command or Settings > Apps > Default apps.

In some cases, Microsoft Notepad or other Win32 programs cannot be set
as the default.

Workaround

In some cases, attempting to set application defaults again will succeed.

Microsoft is working on a resolution and estimates a solution will be
available in late November 2018.

Sources:
October 9, 2018—KB4462919 (OS Build 17134.345)
Microsoft Broke Windows 10’s File Associations With a Botched Update

Update

This problem should be resolved with the release of the KB4467682 Windows 10 Quality Update, which will increment the operating system build to 17134.441:

Addresses an issue that prevents some users from setting Win32 program
defaults for certain app and file type combinations using the Open
with… command or Settings > Apps > Default apps.

Sources:
November 27, 2018—KB4467682 (OS Build 17134.441)
Microsoft Fixes Windows 10’s File Association Bug, Unless You’re Using the October Update