I cannot override it David. It is very objectionable because it offers no options. It seems to be promoting a paid for feature so why can it not be deactivated? Does nobody think at Avast? If Avast mistakenly blocks trusted good browser extensions, the result will be chaos for users.
It isn't promoting a paid service - no idea what that might be if it were - as it doesn't say what that is.
First we have to identity what this 'farcical feature' as this would appear to be the Web Shield doing its job, something other than you making the connection (which it considers suspect) But why it is called URL Phishing is beyond me. Which is why I mentioned that the 'see details' might cast more light on the reason.
I think this is more likely that you aren't actually making that connection, but the extension is for whatever reason that might be (phoning home, etc.).
I have no idea why it is that you use this add-on, I use uBlock Origin, uMatrix, Disconnect, Privacy Badger and DuckDuckGo add-ons and they don't appear to have any of these adverse effects in avast. There are times when they break the functionality of a site because of what they block, but no impact on avast
Again as I mentioned this appears to be two security products clashing, given what is said by netcraft:
Real-time protection from malicious sites including phishing, fake shops, and malicious scripts such as JavaScript skimmers and cryptocurrency miners.
So in effect it is trying/doing what the web shield is doing intercepting connections to try and check if they are malicious.
I can't understand why you haven't mentioned this before when using Avast or is this since you started using Netcraft, or weren't you using the Web Shield ?
As mentioned you have choices, excluding the URL path in the alert in the UI, Menu > Settings > Exceptions > Add Advanced Exception and enter the url path in the alert window.
Or stop using Avast (oh forgot you tried that) or disable the Web Shield Or Netcraft as Avast and the Web Shield (plus other shields) should protect against what Netcraft seeks to protect against.