Ghost is correct, the ONLY thing that can cause it to not use the AutoUnattend.xml is if it is missing, skipped or you bypass it in another way. I have video evidence of it all working, so it would be impossible for it to fail with the files I shared, unless your not using a Windows 10 x64 with Windows Defender and/or your AV disabled to build it on - as I've not tested this. If you edited the Autounattend.xml file to have your region, double check it first. unless it's not skipping all the other components and asking for keyboard, networks, enabling cortana etc.
i dont have a AV and im using en_windows_10_enterprise_ltsc_2019_x64_dvd_74865958 the one you shared .im not sure whats going on .im using VirtualBox_v6.1.4-136177
https://superuser.com/questions/764190/autounattend-xml-not-being-recognized-in-virtualbox The above is a possible cause, it may also be the Virtual Machine you made, you may also not have enough RAM, I have no details from you to figure out what it could be. instead I'll share a VirtualMachine for you to import. -EDIT- If you extract the below zip and open the .ova it'll make a working VM, all you need to do (apart from setting it's drive/path to make the VM on) is to configure the Last20 ISO file in the Virtual DVD drive., It'll then boot and install fine.
Because you haven't deleted or formatted the automatic GPT partitions that have the previous OS's in the boot config on them: Notice the FAT32 disk and it's data, it has no drive letter set, but that is where the boot config is. Option 1 You could delete the Recovery (500mb), FAT32 (100mb), Other (16mb) and the NTFS (Windows) disk), then during installation you pick Unpartitioned space, this will remake those 4 partitions without data. Option 2 format all the disks listed above instead (May work I've never tried) Option 3 (Quickest/FIX) is use BCD edit or EasyBCD to remove one of the menu items. And yes that is my only usable HDD (120gb SSD), I also have a 2TB HDD but it's doing the tick of death randomly everyday now, so I've not been working on much/anything I don't want to lose anything that is on it before I get a chance to back it up when I can afford to get a reliable HDD. The other disk is my family photos/video.
I always unplug all my other hard drives except the OS drive and DVD, then I nuke the drive I want to install on when installing a fresh copy of any windows, for me it cuts down on issues like this, puts all the install on that 1 drive. I know everyone has a different setup for desktop PC, rather 1 SSD and a few spin drives, or like me with 2 SSD's and 3 spin drives, the 2 SSD's are OS drives only. 1 is Win 7 Pro x64, the other Win 10 LTSC at 250GB each. I also have 3 2TB spin drives. Its easy to forget that a clean install of windows will use whatever it feels to use to put Recovery, Boot, etc.. on. This is when I make sure that its done the way I want it to be done, by unplugging all drives except the 1 I want to install to, then nuke that drive completely. As said everyone has a different desktop PC setup, just depends on how to manage it for no issues will make life easier.
