Gadget export
To export the UserLinkAvatar gadget, click on "Download" button, save the downloaded file, go to Special:Import on destination wiki and upload it. Then add the following to MediaWiki:Gadgets-definition page:
* UserLinkAvatar[ResourceLoader|default|type=general|dependencies=user.options,ext.gadget.jQueryLazyload]|UserLinkAvatar.css|UserLinkAvatar.js
You must have appropriate permissions on destination wiki (including the right to edit system messages) and import from file uploads must be enabled.