From 1.41.5b2 and above, it works on non-"trusted" sites with right-clicking the link, there will be an entry on the contextual menu to import the list.
For older versions of uBO, you can already use the old way:
Thanks for your incredibly fast response and help. (Do you have a notification when your username is invoked in HN?)
And of course, thanks for uBO!
In my case, the issue is that GitHub doesn't allow the apb|ubo protocol in links. However, no problem, I can use the method with "subscribe.adblockplus.org". Yet, subscribing from contextual menu is a great feature.
For older versions of uBO, you can already use the old way: