Just for information how to add a Browser Extension subscription - e.g. uBlock Origin
Adding via Right-click
You can subscribe to 3rd-party filter lists by right-clicking on a link for them and selecting “Subscribe to filter list…” from the contextual menu. This works regardless of the site on which the link is hosted.
Regards
Thank you. I will add these steps to the How To Use? page soon.
I haven’t tested all the clients myself but wherever possible we should provide a one-click solution.
I don’t know about one click, but maybe two clicks will do it. 
For example, adding the “Dangerous Websites Warning List” from
The List is also used by private DNS service providers – quad9 and nextdns.io.
https://cert-polska.github.io/adblock-domain-list/
First click with the left mouse button
<a href="abp:subscribe?location=https://hole.cert.pl/domains/v2/domains_adblock.txt&title=https://hole.cert.pl/domains/v2/domains_adblock.txt"> Add list </a>
Second click with the left mouse button**
Tested on Firefox 147.0.3 (64 bit)
Regards
