Yes, but in this context we’re talking about “web apps,” meaning the web address you’re using to connect to lemmynsfw content. There’s the standard lemmynsfw.com, but you can also log in and browse the exact same instance from websites like vger.app (which lets you log into multiple instances at once and gives you a much cleaner UI just like a standalone app). The link earlier lists every app and web app that works with Lemmy, and you might try experimenting with those alternatives to see if any of them give you an easier time uploading. If you want tech support, though, you’re going to have to tell us the web address you’re typing in because the error suggests that it’s not lemmynsfw.com itself but rather one of the many web apps that can do the same thing.
Cool! That’s useful, and rules out Kyle’s initial hypothesis. Issue seems to be with Lemmynsfw.com’s website rather than the instance’s backend (we hope), so I’d email the mods (contact@lemmynsfw.com). In the mean time, maybe try Voyager (website you can open from any device), Sync for Lemmy (if you’re on Android), Boost for Lemmy (also for Android), or browse the full list of apps by platform, popularity, and even open/closed source license type. If it’s a frontend issue, switching that up should help.