I would be glad to have a “hello world” example here, it’s not obvious to me how to build a .wasm from a .f90 file.
Something along the line of Compiler un nouveau module C/C++ en WebAssembly - WebAssembly | MDN, but with Fortran write instead of C printf.
There is also an interesting resource here that uses flang-new-15, but the introducing example is a calculation, not a simple write.