With Fedora 26 I had sporadic problems with the system crashing at the first kernel mode switch, before entering the LUKS passphrase at boot time, but I could hit reset and usually the second time it would work. With Fedora 27 this happens to me consistently every time. The only way I can successfully boot is to use "nomodeset" on the kernel command line, which then causes issues for my X session. My system has Asus Sabertooth 990FX R2.0 motherboard, AMD FX-8350 CPU, and Radeon HD 5850 graphics card. I'm running Fedora 27 with kernel 4.15.3-300.fc27.x86_64. Fedora Bugzilla shows someone else having that problem with HD 5450. Maybe its a general Evergreen problem. https://bugzilla.redhat.com/show_bug.cgi?id=1474044
Replaced Radeon HD 5850 (midrange Evergreen) with Radon R7-240 (low-end GCN 1st gen), and it boots fine without needing to remove rhgb or add nomodeset.
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