Not knowing your geo, if in the US - one barrier is the engineering certification process which is above and beyond an engineering college degree. This applies to civil engineering at least if not other fields.

As a software engineer by training myself, personally I’d leverage your existing skills to apply to adjacent interesting fields as what doesn’t need software at this point. After you have a foothold in a new space you can pivot depending on interest from there. I think it is sort of hard at 40 to restart the process. - I’m older than you.