https://github.com/llvm/llvm-project/blob/main/flang/docs/Hi...
Maybe the work in Swift (SIL), Rust (MIR), Julia (SSAIR) that were partially the inspiration for MLIR, alongside work done at Google designing Tensorflow compiler?
The main goal being an IR that would accomodate all use cases of those high level IRs.
Here are the presentation talk slides at European LLVM Developers Meeting back in 2019,
https://llvm.org/devmtg/2019-04/slides/Keynote-ShpeismanLatt...
Also you can find many general purpose enough users around this listing,
C and C++ took over many of the use cases people where using Fortran for during those decades.
In 2025, while it is a general purpose language, its use is constrained to scientific computing and HPC.
Most wannabe CUDA replacements keep forgetting Fortran is one of the reasons scientific community ignored OpenCL.