WoWUp works perfectly fine for me. Sure there was a bit of a glitch when Curse pulled the plug on their access to their addons - but that had been expected for a long time … and multiple times actually, as Curse would give a date when they were switching to the new API and then failed to do so.
Obviously it does mean that none of my addons get updated from Curse via the addon manager, but I have loads of addons, only 7 of which I could not get from anywhere else, two of which have already said they’re planning on hosting elsewhere (Details! being one of them), 2 I can live without, and the others I’ll keep using until they break and then either look for alternatives, decide if I can live without, or just update manually.
WoWUp allows you to not only search for and keep updated addons from Wago, Tukui and wowuphub, but also import directly from URL from wowinterface and github - which it will also then keep updated.
Essentially, it’s actually better than the Curse addon manager because you can keep addons up to date from multiple sources, the only down side being that you’re unable to keep Curse addons up to date.