I had a similar issue with my system when I installed kernel 6.3.4.
I found the issue was caused by an option in the kernel command line.
With trouble shooting and trial & error I found that this command line works for me.
GRUB_CMDLINE_LINUX="rd.driver.blacklist=nouveau modprobe.blacklist=nouveau nvidia-drm-modeset=1 rd.lvm.lv=fedora/root initcall_blacklist=simpledrm_platform_driver_init"
While the previous command line that had worked for several kernels (all the way back to the early 5.X kernels) failed and caused the hang noted. That line was:
GRUB_CMDLINE_LINUX="rd.driver.blacklist=nouveau modprobe.blacklist=nouveau nvidia-drm-modeset=1 rd.lvm.lv=fedora/root initcall_blacklist=simpledrm_platform_driver_init kvm_ignore_msrs=1"
Note that the removal of the kvm_ignore_msrs=1 was what fixed booting for me.
The system failed to complete the boot and hung as noted with the underscore on screen before that option was removed.
In the troubleshooting process I had also removed the initcall_blacklist option and that allowed the boot but only displayed a grey screen and never got to the login screen. My final functional command line is as noted above. (Tested by editing the command line from the grub menu, made permanent by editing /etc/default/grub then running grub2-mkconfig -o /boot/grub2/grub.cfg)