After selecting to boot from CD, I pressed Shift-F8 prior to selecting installation of Windows 98 from second menu to enable confirmation of every command prior to its invocation. I used this to start every command but "INSTALL=MODE.COM CON CP SELECT=xxx" with "xxx" matching your local codepage, e.g. 850 for latin-1 used in Western Europe. This implies failed selecting your local keyboard layout in DOS mode, but this might be okay.

So I succeeded with my recent issue. If your harddisc is larger than 512 MB you'll need to reboot and thus pass the previous process a second time. Then it is formatted and scanned prior to starting GUI for copying files from CD to harddisc.

NOTE! First installation crashed then. If you see "Fault outside MS DOS Extender" try shutting off your VM, then disable VT-X option and start it again.

I succeeded to install Windows 98 (not SE) in VirtualBox using Bootable CD this way.