HandBrake

Perhaps MKVToolnix. Though I don't know whether MKV files will play inline on Discord or not.

MKVToolNix, but indeed MKV won't work for Discord on most devices. You can use it to split your source video and then feed the pieces to HandBrake individually.

If the source is a DVD, MKVToolnix won't be able to split it easily, or did they add DVD structure support at some point like they did for Blu-ray?

Under macOS you could split the output with MKVToolnix, then use Subler to convert each piece to MP4. I think there may be an app similar to Subler for Windows, but I can't remember which.

I think there may be an app similar to Subler for Windows, but I can't remember which.

VideoRedo
The new version 6 is a beast with new formats and controls.

Well, i'm on MS Windows, and i was hoping for something simple like how zip files get split in WinRAR or 7-Zip, just put in a vid and it splits voila! But i have to give you guys a lot of respect because i've learned just how complex this is and how well your software deals with it, i've use MPlayer for vid playback for years for example, and that code never rests always more updates going on, but looks the same to me lol!