I'm trying to create a modpack using the technic launcher which specifically needs you to use the forge universal.jar and extract it to create the pack. However, whenever I try to run the file as instructed, it simply doesn't open, and only shows a loading cursor for a moment before nothing else. Task Manager shows no java processes are running when this happens. I tried using cmd to manually run the file like some other threads have said, and got back "no main manifest attribute, in forge-1.14.4-28.2.19-universal.jar"

Every other thread I've searched through online to try and find a solution has either been for a different situation or simply said "don't use the universal then", which is not an option for me. I've tried using the other methods of installing it, and when the game runs, it runs fine, but without forge or any sign of it being present.

The universal is no longer what starts the server.

Use the installer.

As I said, I need to use the universal to extract the files. I've tried using the installer and the extract option on there the same way already, and as I said originally it just starts minecraft without forge.

No you don't. Use the installer. And use the vanilla mojang launcher.

I'm specifically trying to use this launcher to create a modpack, so using the vanilla launcher is not an option here. Yes it works fine using the vanilla launcher with the normal installer, but that's not what I'm trying to do here.

That is your problem, the technic launcher is super old I doubt it supports forge on modern versions. There is literally no way to 'just use the universal' that is not how any of this works anymore.

We do not support 3rd party launchers.

There is nothing in those launchers that is required for you to make a mod pack. You can make it quite easily on the vanilla launcher.