I'm not a total newbie when it comes to VirtualBox... I've used it for many years on multiple computers using multiple host OSes. This computer runs Windows 11 and has several working guest OSes in VB. I'm trying to check out Devuan though and I can't seem to figure out the secret sauce to make it bootable after install. Every variation I try, after ejecting the installer ISO and rebooting, I get:

There are a lot of installation questions but I choose the defaults which seem sensible. I've tried telling VB it's both a "Debian" OS as well as "Linux - Other". Nothing seems to make a difference. Does anyone know of the secret sauce necessary to get Devuan working as a guest OS? Thanks!

VirtualBox Version 6.1.34 r150636 (Qt5.6.2)

Win11 - HyperV disabled

One caveat, I am only running W10...
I assume that you are not using UEFI and it looks like you did not install grub to the MBR.

I just installed it using linux debian (64 bit). At the end of the installation the installer defaults to manually install but I selected the second option of /dev/sda.

I actually did select to install grub to the MBR (vs the partition, etc) when that option came up, so that's not it. I'm wondering if I need to walk through and outline every option I chose (99% of the time, just the defaults though).

That might help.