So, a few years back I installed AntiX-21 onto a 20+ year old onto an old WinXP laptop both as a fun project and to get some practice with Linux. It worked fine, and I mostly used the resurrected laptop to watch youtube videos and listen to podcasts, which was just a fun novelty to do on such an outdated machine. Obviously I couldn't do Youtube in a browser, but I could take URLs and watch videos with VLC in 360p.
At one point VLC video playback stopped working entirely and I could only do audio, I assume because of changes to Youtube. I tried using the AntiX Updater, but even after updates playback wasn't working. Looking at the version numbers of the updated versions of SMPlayer, VLC, etc I noticed they were still not the latest versions available.
I went to the repo manager and added a bunch of repos until I saw more up to date versions of VLC and other programs in the package manager, then used AntiX Updater again and said yes to the over 1,200 updates.
Things didn't go smoothly. The updates were constantly interrupted by errors but I kept restarting the update process until I had to log off for the night. When I logged back in the following day, the desktop I had been using was missing and I could no longer connect to the Internet because ConnMan was broken. I managed to connect to my Wifi with CENI and kept trying to get the rest of the updates done. I just couldn't get ConnMan to update no matter what so I rebooted the laptop again. This time the bootup process was filled with error messages and I could no longer log in at all. I'd enter my username and password and it'd just loop back to the login screen.
I'm pretty sure my AntiX install is bricked now. I assume I should try wiping the Linux partition and reinstall?
I just wanted the latest version of VLC 
Mixing a bunch of packages from incompatible repos just produces conflicts, and it's not just because apt is complaining, programs actually have constraints about library versions they need to work and so on.
You can try to set your apt sources to one and only one repo that actually works (probably a newer one like Debian unstable is better, downgrading isn't really supported), then remove all the packages except the base system, and then upgrade and hope that works. Then start installing stuff again.
But if this does not work you're going to need to reinstall, so just reinstalling is maybe easier. I would recommend trying to fix it though, for the challenge.
You'll need to do this from the virtual console w/o graphics (that's not part of the base system), and you probably want a wired network connection. I hear you can use an android phone over usb for that somehow, in case you don't have anything else.
There are cases where trying to repair a broken Linux system can be a good learning experience (i.e. it stopped booting because a kernel driver is missing, you somehow managed to uninstall util-linux, you messed up some important config files in /etc, you managed to install a version of libc which is not ABI compatible with the rest of the system), but I imagine this install is so cooked that it would be more practical and educational to just do Linux From Scratch instead. :)
It is good to learn how to fix things when they break, but learning to fix a problem created by several arbitrary steps which cannot even be replicated is not the most useful knowledge in the world. And then there is always the lingering possibility that something minor is still screwed up causing problems which nobody else in the world will ever run into, which you cannot find any documentation for in a web search.