I have a similar problem. For me the Ubuntu 20.04 installer would consistently crash at 90% (regardless of which hard drive I installed it to). When I followed the instructions to report the bug, it led me here.
I was able to circumvent the problem by choosing "minimal installation" and NOT "download updates while installing". That made the installation succeed.
It might be caused by bad hardware on my system. I don't know.
I have a similar problem. For me the Ubuntu 20.04 installer would consistently crash at 90% (regardless of which hard drive I installed it to). When I followed the instructions to report the bug, it led me here.
I was able to circumvent the problem by choosing "minimal installation" and NOT "download updates while installing". That made the installation succeed.
It might be caused by bad hardware on my system. I don't know.