Oh thanks!

Actually I want use CUDA for Blender...

EDIT

Oh boy you are a genius... I would really like being able to open a code, understand it, and eventually fix it!!!

By the way I think I solved the issue leaving the second disk in a partionless state, other thing is creating /boot outside of the btrfs filesystem; I did the same on my real hardware (WOW!!! ) and it worked.

Soon my recommendations or at least what I did... :-P

I re-did the installation and this time the issue doesn't happen, perhaps because I did all my steps clearly and in the right sequence, and now I have Devuan on a Btrfs RAID using subvolumes as partitions:

gnuser@devuan:~$ lsb_release -a
No LSB modules are available.
Distributor ID:	Debian
Description:	Devuan GNU/Linux 3 (beowulf)
Release:	3
Codename:	beowulf

gnuser@devuan:~$ mount | grep btrfs
/dev/sdb1 on / type btrfs (rw,noatime,discard,space_cache,autodefrag,subvolid=268,subvol=/@)
/dev/sdb1 on /home type btrfs (rw,noatime,discard,space_cache,autodefrag,subvolid=270,subvol=/@home)
/dev/sda3 on /media/snapshots type btrfs (rw,relatime,space_cache,subvolid=5,subvol=/)

gnuser@devuan:~$ sudo btrfs fi df /
Data, RAID0: total=4.00GiB, used=3.64GiB
System, RAID1: total=32.00MiB, used=16.00KiB
Metadata, RAID1: total=256.00MiB, used=125.92MiB
GlobalReserve, single: total=16.00MiB, used=0.00B
gnuser@devuan:~$ sudo btrfs fi show
Label: 'btraid'  uuid: cf6cf3c5-f308-46b8-b4e8-dea7ad870436
	Total devices 2 FS bytes used 3.76GiB
	devid    1 size 16.00GiB used 2.28GiB path /dev/sdb1
	devid    2 size 16.00GiB used 2.28GiB path /dev/sdc

Label: 'snapshots'  uuid: bcbe0d7f-14c9-4ad4-86c4-27362d64ef93
	Total devices 1 FS bytes used 3.66GiB
	devid    1 size 5.59GiB used 4.51GiB path /dev/sda3

gnuser@devuan:~$ lsblk 
NAME             MAJ:MIN RM  SIZE RO TYPE  MOUNTPOINT
sda                8:0    0   16G  0 disk  
├─sda1             8:1    0  524M  0 part  /boot/efi
├─sda2             8:2    0  525M  0 part  /boot
├─sda3             8:3    0  5.6G  0 part  /media/snapshots
└─sda4             8:4    0  9.4G  0 part  
  └─sda4_crypt   254:0    0  9.4G  0 crypt 
    ├─vgcr0-swap 254:1    0  3.7G  0 lvm   [SWAP]
    └─vgcr0-enc  254:2    0  5.7G  0 lvm   /mnt/private
sdb                8:16   0   16G  0 disk  
└─sdb1             8:17   0   16G  0 part  /home
sdc                8:32   0   16G  0 disk  
sr0               11:0    1 1024M  0 rom   

I am almost ready to install Devuan on a real hardware!!!

Yes of course, I also installed the Guest Addition but no traces of vboxdrv, and vboxsf and vboxvideo exist as modules but won't load even if I put in /etc/modules/modules.conf.

On the same HOST I have also Debian testing which works perfectly with all these features available...

Thanks for all these information, but I have been using Debian testing as a rolling distro so far, and I feel comfortable with it, you probably said me the same on the Debian forum... :-p

Epic fail...

I must dig into it... But I found the Refract Installer quite convoluted I hope this will be more user friendly.

I am ok with unexpected breakage, the amount of issues with Debian testing are really few compared with Debian Sid, I am also thinking to use BTRFS to handle issues with the updating and eventually revert to the previous status.

I am still figuring out the best option, but one thing is sure I don't like systemd as much as I don't like stable release distro.

This exactly what I am trying to do... Testing/Ceres... Just Unstable is too extreme for me, I had a lot of headaches with Debian Sid unless Devuan, since is delayed respect Debian, doesn't have the same issues and get all packages already fixed from upstream.

It is "safer" using Ceres compared "theoretically" with Sid?

Thanks for video screencast I missed that option, I have been always creating the encryption through the menu on top. Honestly I am pretty new to encryption I started using on POP and I used this method:

https://write.snopyta.org/gnuserland/tu … encryption

Now I am doing some test with the refracta installer but it I find it a little bit convoluted for my tastes...

I used to do my partitions manually once, when I had plenty of time available, then I decided that a smart installer is wise and smart thing and I like very much using it, more is complete the better. And the Debian installer is really good, beside the fact that works on several platform can perform LVM and encryption; others derivatives like Ubuntu Desktop, Mint, POP!_OS, Elementary or Linux MX cannot handle installation on multiple disks. The only exception is the Ubuntu server installer.

Other distros like gentoo, also arch, are better designed to be handled manually. Recently I discovered KISS which follow the same approach, I'd like to play with it but I don't think will ever have time...