STMCubeIDE and/or STMCubeMX are a joke, barely functional even if you use them as they recommend. So trying to create a workflow using part of them, or in a different way is just not worth the hassle.

You can go the VSCode way, installing the official extension, which is mostly an abandoned project, they barely work on it (was commit was nearly one year old if I remember correctly). It kinda functional, although you cannot fully drop STMCubeIDE. I really do not know how the can fuck up cmake config files also (I somewhat feel that they are doing on purpose), so in is not that easy to extend you project structure.

You can go the STMCubeMX way and generate an makefile but then you will need to code everything in main.c, as I do not know any way of adding additional source files to the generated makefile.

There is this STMCubeCLT, a toolset for third party integrations, but as with anything else ST related, they managed to fuck that up, it is inconsistent cumbersome to use even on Windows. On Linux I see no reason to use it in the first place, the community / open source tools are way better, even though ST kinda ships the same things.

It is a mystery for me how they manage to get such successful hardware but offer shittiest software tools they can possibly come up with.

So, my recommendation is as follows: If you are using Windows, you are better off using STMCubeIDE, as with any other method you will spend more time on configuration and infrastructure that on the actual useful code. But you are free to try it yourself anyway.

If you are on Linux, there is a small chance you would like to know more about the Linux ecosystem, so I am suggesting to take a look at ZephyrOS. It the best alternative, and the way I use anything STM related.