I use 2 pieces of software.

One is called "Ultimate Vocal Remover". Free and available on GitHub. It's a piece of software that seperates the vocals from the instrumentals. It's a little bit complicated to setup but once you got it setup you can just drag and drop the original audio in and then it spits out all the different tracks and stuff.

Then I use another one called "KdenLive". Also Free download. This one is basically a video editor. And can be used to create the text for lyrics. It can also do animations and such. Admittedly it's a lot of work if you want to animate the lyrics haha. You basically have to line up the highlighting with each syllable in the word. Doing it without highlighting is a lot easier but also less precise. So pros and cons. ( I'm the meticulous type haha, it's just time consuming).

A friend of mine helped research this for me as they too wanted to do karaoke videos. And then they taught me while showing me their screen. We're considering creating a tutorial video for others but we haven't got around to it yet.

;-)

Lookup "Impulse Karaoke" on YouTube if you want to see my work. Though currently I only have 2 songs so far. I'm trying to do 1 song per month. I have a list I'm working off of. We'll see what happens after that.