Hi I'm having a similar issue. In my case is a white screen; probably black screen is related with the nocturne mode.
I use two IOS devices, iPhone and iPad, both devices are in english and have IOS 14.5 and Evernote version 10.9;
I'm using the basic license. I did some tests using wifi and mobile networks.
In web version, I did steps for "what is new"; but after that works fine. But it not solve ios version.
I tried uninstall and install again with no success.
Thanks
Eduardo