I finally got around to writing an actual guide for this.

1. First check if you have IPv6 support by visiting https://ipv6.icanhazip.com/. If it says there's a connection error, don't worry, some ISPs have IPv6 but it isn't enabled in your router by default. Try visiting your router's admin panel (usually http://192.168.1.1/ or http://10.0.0.1/) and seeing if you can enable IPv6.
2. Figure out your IPv6 prefix by visiting the above website on multiple different devices. The part that doesn't change is your router's assigned prefix, and anything after it can be changed to whatever you want for each device. Most ISPs give you a /64 prefix, meaning anything from xxxx:xxxx:xxxx:xxxx:0000:0000:0000:0000 to xxxx:xxxx:xxxx:xxxx:ffff:ffff:ffff:ffff is available.
3. Set a fixed IPv6 address for the device you want to watch YouTube on by going to your computer's network settings and setting IPv6 mode to manual, then adding a fixed IP address using the prefix you previously obtained.
4. Set the preferred network method to IPv6 if possible.
5. Change your IPv6 address every time YouTube blocks you.