Kernel 5.11.xx not booting, need to fallback to 5.8

[robert]

Hi there

I have a dell xps 17 with Ubuntu 21.04

for some time now, I can not boot into the default kernal anymore, but have to 
use an older 5.8.xx kernel.

I just get a small blinking cursor and the booting stops there ..

can anybody of you give me an idea, how to fix that.

thanks

robert

the running kernel:

root at kappi3:/etc/apt/sources.list.d# uname -r
5.8.0-50-generic

the list of installed kernels:

root at kappi3:/etc/apt/sources.list.d# dpkg --list | grep linux-image
rc  linux-image-5.11.0-16-generic 5.11.0-16.17 amd64        Signed kernel image 
generic
ii  linux-image-5.11.0-17-generic 5.11.0-17.18 amd64        Signed kernel image 
generic
ii  linux-image-5.11.0-18-generic 5.11.0-18.19 amd64        Signed kernel image 
generic
rc  linux-image-5.8.0-18-generic 5.8.0-18.19 amd64        Signed kernel image 
generic
rc  linux-image-5.8.0-19-generic 5.8.0-19.20 amd64        Signed kernel image 
generic
rc  linux-image-5.8.0-20-generic 5.8.0-20.21 amd64        Signed kernel image 
generic
rc  linux-image-5.8.0-21-generic 5.8.0-21.22 amd64        Signed kernel image 
generic
rc  linux-image-5.8.0-22-generic 5.8.0-22.23 amd64        Signed kernel image 
generic
rc  linux-image-5.8.0-23-generic 5.8.0-23.24 amd64        Signed kernel image 
generic
rc  linux-image-5.8.0-25-generic 5.8.0-25.26 amd64        Signed kernel image 
generic
rc  linux-image-5.8.0-26-generic 5.8.0-26.27 amd64        Signed kernel image 
generic
rc  linux-image-5.8.0-28-generic 5.8.0-28.30 amd64        Signed kernel image 
generic
rc  linux-image-5.8.0-29-generic 5.8.0-29.31 amd64        Signed kernel image 
generic
rc  linux-image-5.8.0-31-generic 5.8.0-31.33 amd64        Signed kernel image 
generic
rc  linux-image-5.8.0-33-generic 5.8.0-33.36 amd64        Signed kernel image 
generic
rc  linux-image-5.8.0-34-generic 5.8.0-34.37 amd64        Signed kernel image 
generic
rc  linux-image-5.8.0-36-generic 5.8.0-36.40 amd64        Signed kernel image 
generic
rc  linux-image-5.8.0-38-generic 5.8.0-38.43 amd64        Signed kernel image 
generic
rc  linux-image-5.8.0-40-generic 5.8.0-40.45 amd64        Signed kernel image 
generic
rc  linux-image-5.8.0-41-generic 5.8.0-41.46 amd64        Signed kernel image 
generic
rc  linux-image-5.8.0-43-generic 5.8.0-43.49 amd64        Signed kernel image 
generic
rc  linux-image-5.8.0-44-generic 5.8.0-44.50 amd64        Signed kernel image 
generic
rc  linux-image-5.8.0-45-generic 5.8.0-45.51 amd64        Signed kernel image 
generic
rc  linux-image-5.8.0-48-generic 5.8.0-48.54 amd64        Signed kernel image 
generic
rc  linux-image-5.8.0-49-generic 5.8.0-49.55 amd64        Signed kernel image 
generic
ii  linux-image-5.8.0-50-generic 5.8.0-50.56 amd64        Signed kernel image 
generic
ii  linux-image-generic 5.11.0.18.19 amd64        Generic Linux kernel image
ii  linux-image-generic-hwe-20.04 5.11.0.18.19