I had the same problem, I am aware that downgrading resolves the bootstrap problem, but I take it as a challenge to find a solution with the newer version. I most often do find one, but in this case it required for me to import some FontAwesome libraries, and found myself stuck there, so I decided to skip the exercise. I hate downgrading, and if you want to be compliant with your projects, you need to upgrade frequently and resolve issues.
Apart from updating the videos, @Mosh you could also provide the code material at the beginning of each section, it would make it possible for me to continue (if I skipped some exercise) and if I ever want to go back in the course and revisit some part of it, I can easily go into the section, download the code and start from there.
I bought a lot of your C# courses on udemy, and I still go there very frequently to revisit some concept, or to see what the best practice is around something.