@gorhug I have a Steam Controller too that I would love to play the game with (aiming is so bad with a joystick) and this issue is completely foiling those plans...

Interestingly, while using mouse and gamepad at the same time there is no stuttering whatsoever. At this time, the UI glyphs are locked to keyboard/mouse. It is only when the mouse is released (or finger lifted off the right touchpad on the Steam Controller) while the player is still moving (left joystick in use), or doing any other controller action, that the freeze and mute occurs, which again coincides with the UI glyphs changing (this time back to gamepad glyphs).

With this observed behaviour, I believe it can be said with rather high certainty that the issue really does arise from the UI switch specifically, and not from using the input methods at the same time.

Also, to supplement your request, allowing the player to lock in either kb/m or gamepad UI glyphs is in my opinion an essential feature for accessibility and adjusting the user experience to suit everyone's needs, and would be really high on my wishlist too for Steam Controller playability. It might even fix the entire mute/freeze issue.

This appears to be a commonly-occurring problem independent of computer spec, I can confirm I experience it too.
Hybrid input is enabled and whenever I touch my mouse or keyboard, the game freezes and mutes for a second. When I then touch one of the inputs on my controller again, it freezes and mutes again.

This coincides with all the control glyphs being swapped out for keyboard/mouse glyphs (or kb/m to controller), so perhaps it has to do with the game accessing some compressed/encrypted resource file on disk?

It does the same when leaving photo mode. Although of course here there is no switching of control glyphs, it does appear to reload all terrain textures as I see all surfaces around Eivor get blurry and then quickly sharpen again.
This would again be reading from a resource file on disk, so I really suspect something to do with file access or decryption is at the source of this problem.

It would be wonderful if Ubisoft could look into this.

@gorhug I have a Steam Controller too that I would love to play the game with (aiming is so bad with a joystick) and this issue is completely foiling those plans...

Interestingly, while using mouse and gamepad at the same time there is no stuttering whatsoever. At this time, the UI glyphs are locked to keyboard/mouse. It is only when the mouse is released (or finger lifted off the right touchpad on the Steam Controller) while the player is still moving (left joystick in use), or doing any other controller action, that the freeze and mute occurs, which again coincides with the UI glyphs changing (this time back to gamepad glyphs).

With this observed behaviour, I believe it can be said with rather high certainty that the issue really does arise from the UI switch specifically, and not from using the input methods at the same time.

Also, to supplement your request, allowing the player to lock in either kb/m or gamepad UI glyphs is in my opinion an essential feature for accessibility and adjusting the user experience to suit everyone's needs, and would be really high on my wishlist too for Steam Controller playability. It might even fix the entire mute/freeze issue.

This appears to be a commonly-occurring problem independent of computer spec, I can confirm I experience it too.
Hybrid input is enabled and whenever I touch my mouse or keyboard, the game freezes and mutes for a second. When I then touch one of the inputs on my controller again, it freezes and mutes again.

This coincides with all the control glyphs being swapped out for keyboard/mouse glyphs (or kb/m to controller), so perhaps it has to do with the game accessing some compressed/encrypted resource file on disk?

It does the same when leaving photo mode. Although of course here there is no switching of control glyphs, it does appear to reload all terrain textures as I see all surfaces around Eivor get blurry and then quickly sharpen again.
This would again be reading from a resource file on disk, so I really suspect something to do with file access or decryption is at the source of this problem.

It would be wonderful if Ubisoft could look into this.