You can find videos on Youtube, it's like an IDE where you would do everything in a user interface with menus, but the interface is a 25x80-char screen only :-) Everything is "almost" similar to a Unix system, but with different names, files are called "datasets", there are very few tools, but every one of them has a language to do very complex tasks...
The goal of SuperBOL (https://superbol.eu) is to allow companies to migrate from mainframes to Linux workstations, to get a "modern" experience of development and deployment.
Indeed, mainframes are hard to get access to, and require a training by themselves, I have worked on Linux and Windows for years, and development on a Mainframe has nothing in common :-)
I think the problem of COBOL is not only the lack of COBOL developers, it is the lack of expertise in COBOL environments, because they have become obsolete (both on mainframe and proprietary tooling for Linux/Windows). By providing a modern environment on Linux for COBOL, our goal is to solve the hardest part of the problem, as learning COBOL itself is not so hard for existing open-source developers...
We are among the major contributors to GnuCOBOL, we use https://github.com/OCamlPro/gnucobol to review our contributions before pushing them on the SVN of Sourceforge.
Cobolworx is indeed working on a gcc frontend for COBOL. It's an impressive work (that was presented at FOSDEM this year), but less mature than GnuCOBOL, and tied to gcc, whereas GnuCOBOL can work with any C compiler (llvm, msvc, etc.) by translating COBOL to C.
Though we desig SuperBOL to work with GnuCOBOL, it could also be used with GCOBOL when it will be officially stable.
COBOL is not dead, but it's difficult to get access to, because there is almost no open-source tooling around it for Linux. We (OCamlPro) have created a project, called SuperBOL, to create an open-source environment around the GnuCOBOL open-source compiler (that is now very mature and used by companies). We have already released the VScode extension with an LSP for COBOL to get a modern IDE, and we are working on other tools, mostly depending on our customers.