re-installing AP won’t do nothing for nik, you need to uninstall nik collection completely, then install your google version and set your AP plugin again.
installing newer version of nik overwrite your existing version, it says that when you install it.
That’s the problem, NilkCleanup (that only is applicable to 2018, 2, 3, 4, 5, 6) - is not cleaning up 100% - if I point the app back to the original google plug-in’s it still called for example ─Viveza and wants me to buy it.
Apart from reformatting the complete drive - I am out of options.
You can configure any plugin in AP (Nik or whatever) by opening the Preferences | PS Plugins configuration panel and adding the folder(s) where your plugin(s) are stored. At least in AP 1.x (I didn’t upgrade to version 2 but I don’t see why this setting shouldn’t work in v2). I did this for multiple plugins and I didn’t get any problem.
There is a known bug between Nik 6.0 and Affinity 2.1 where the plugins don’t work. The Nik 6.1 update fixes that bug. But if your versions are anything other than 2.1 and 6.0 then it should all work. And once it works you will find that Nik has advanced hugely, it is much more capable and controllable than the old Google version.