I experienced the same issue, albeit without the complication of a second drive containing another O/S. My workaround was to perform an install without WiFi connectivity and then after completing the install perform the necessary updates and third party driver modifications. The installation consumed much more time due to the latter event unfortunately.
-- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1875911 Title: ubuntu 20 failed install on Dell Precision 5510 Windows 10 - grub- install: error: failed to register the EFI boot entry: Invalid argument. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/grub-installer/+bug/1875911/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs