1Password extension on second instance of Chrome working weird

Luckily enough, I have fixed it 😀. The culprit was the native messaging manifest file. 1Password desktop (it seems) installs the manifest file at the predefined path: ~/Library/Application Support/Google/Chrome/NativeMessagingHosts/com.1password.1password.json, which is under the default --user-data-dir. Since the second instance's --user-data-dir is non-default, there is no one to install the manifest there. The absence of the manifest is the direct reason for the extension being unable to connect to the desktop app.

So, I manually copy-pasted the manifest to the proper location.
The issue isn't a bug at all in the first place. My non-trivial and custom configuration is the thing.