Помогло:
To all who are still struggling with above, this is the solution (as of version 2.122):
Navigate to Jenkins > Credentials > System > Global Credentials
Add Credential
Select Secret Text from dropdown menu
Add description (name of account, reason, etc.)
In secret text box, deposit your Github Personal Access Token (GPAT)
Save and navigate back to Jenkins > Global Configuration
Find your Github Server Access section and select your credentials from it, then click Test Connection
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