My laptop was originally set up to dual boot Chimaera and Windows on separate SSD partitions. Its an EFI system with AMD onboard graphics and Nvidia add-on graphics. I was finding that some programmes I wished to run were demanding more up to date support than Chimaera provided so I already had some bits from testing installed and this was making the system a mess but it was working adequately.  I decided to install Daedalus Preview onto a separate new partition which I set up before I started the install. I used "devuan_daedalus_5.0.preview-20230213_amd64_netinstall.iso" loaded onto a USB stick.

When installing, I told the installer to put Daedalus on the new empty partition. All seemed to go well with the install until I rebooted at the end. Grub came up - but only showed the new Daedalus, (missing the Chimaera and Windows options) and when I tried to run it it froze a few lines into the boot waiting for /dev to be fully populated. I gave it time! I tried the advanced boot option and that got further through the boot process but still froze before the end (about 4 seconds in?).

I solved the grub problem by using the rescue option on the install disc to reach the original Chimaera OS in rescue mode - doing a grub-mkconfig and then a grub-install. That let me back into Chimaera from where I managed to use a chroot to install the nvidia packages onto the Daedalus partition (that solved the first boot freeze) and then the AMD firmware which I believe was the cause of the second freeze. This gave me a working Daedalus. End of Panic.

This took a number of attempts over two days so much confusion and maybe missing vital steps from this report. I am not recommending these solutions but I now have clues for the next time.

Thank you for Devuan. I have used it for several years now and am generally very satisfied with it.