Boot with kernel 6.6.13+ hangs at uevents nomodeset helps, radeon and amdgpu

Brief summary of the problem:

When booting self compiled kernels version 6.6.x the process gets stuck at hardware initialization through uevents. Using nomodeset makes boot complete but without graphics.

https://bbs.archlinux.org/viewtopic.php?id=292265 – with ADMGPU https://bugs.gentoo.org/925861 – my personal one with radeon (TAHITI never worked with AMDGPU)

Hardware description:

• CPU: AMD A8-4500M
• GPU: 00:01.0 VGA compatible controller [0300]: Advanced Micro Devices, Inc. [AMD/ATI] Trinity [Radeon HD 7640G] [1002:9903]
• System Memory: ?
• Display(s): hannspree touch something/ internal TFT
• Type of Display Connection: HDMI

System information:

• Distro name and Version: Gentoo Linux
• Kernel version: 6.6.13, 6.6.18, works on 6.1.67
• Custom kernel: compiled with radeon as module, no conflicting Radeon FB, .config see Gentoo bug ticket from above (make syncconfig from 6.1.67, one kernel with all default options, a second with all N, no difference)
• AMD official driver version: ?
• booting with initramfs and firmware, does not matter whether firmware is builtin/ no modules or with modules and late firmware loading

How to reproduce the issue:

1. Compile
2. Boot
3. Hangs infinitely at uevents (no freeze, NUM key still working, seems to wait for some hardware, no sshd, no TTY)

I already searched through the existing issues, namely

• #3126 (closed) – mine does not boot at all, nomodeset blocks all GPU usage
• #3160 – no switching of UEFI framebuffer to graphics card (normally screen blanks at this stage, returns and proceeds)
• #3207 (closed) – will also try 6.5 but sounds identical, except the blank screen