Definitely. It's reasonable to buy things at cheaper prices, which is basically what Black Friday is famous for. In terms of advice, I suggest you buy the domains/hosting plans along with your online training courses on Black Friday if you have a special offer during that time, since it's probably one of the only times where you receive a potential massive discount.
As for me, I'm not buying anything in particular related to websites on Black Friday, but I have in the past. A couple of years ago, when I wanted to host my own video game server along with a corresponding website, I paid 50% less to buy a package offer on Black Friday, which was an insane save. Again, I fully recommend doing your domain shopping on that day.
