Download binaries for DJGPP cross compiler and unpack it. Change the DJGPP_DIR in CMakeLists.txt to the absolute path of the DJGPP directory.

"clangd understands your C++ code and adds smart features to your editor: code completion, compile errors, go-to-definition and more". To Install, clangd go here.

sudo apt install dosbox

We'll need a A DOS extender

a computer software program running under DOS that enables software to run in a protected mode environment even though the host operating system is only capable of operating in real mode." (Wikipedia)

We'll use CWSDPMI. Download a binary distribution. mkdir bin directory in the source directory and copy the downloaded binary (CWSDPMI.EXE) into it.

mkdir build directory in the source directory. cd into build and run,

cmake ..
make main

compile_commands.json will be created in build directory. Symlink it (or simply copy it) to the root directory. To symlink it, cd to the root and

ln -s build/compile_commands.json .

cd into bin directory. and run,

dosbox -c "mount x $PWD" -c "x:" -c "main.exe"

From build directory

make && cd ../bin && dosbox -c "mount x $PWD" -c "x:" -c "main.exe"

Assemble .asm file with

nasm -f coff <filename>.asm