even if it "works" , it cannot handle most websites. You are very lucky if you find a site where this is working.
A lot of work and very little reward when using this. Just stick with built-in manager, itz much better.
as the developer himself says: "beta". not working here on Arch-Linux. First install is total FAIL. .py file gets truncated during install. tested in ff 59 and ff ESR. both are total FAIL. there should be more info how to debug this simple thing and working examples given, e.g. on which site it even works and where to put the weird stuff with the < and > or whatever. Has some potential though, since both KwalletCLI and GNOME-keyring both are rendered obsolete crap now in current FF v.58 so passFF could step into the fray.
---- hours later ----
OK, I got it to "work" after doing everything manually. I was almost done with programming my own webextension. The py app (called "native" thingy or whatever) install failed 100%
I had to correct the path in the JSON file . Then from add-on menu choose "debug passff" web-extension, see if debugger console shows errors. if need be set breakpoint with CTRL-B , a hidden function.
but even if it "works" - such as "Goto, Fill and Submit" works for website https://identity.kde.org/index.php?r=site/login - the normal ffox passwd manager is much more convenient. you have to enter each passwd manually into the addon, even type the passwd TWO times. what an ordeal. its easier to enter passwd everytime manually than to use this "tool". very, very beta. needs better explanation.
Maybe I'm gonna mod and fork this thing so it becomes useable. In those 4 hours I wasted on this thing, I could have typed thousands of bloody passwords.