VirtualBox 6.1.18 + ConTeXt
Perform OS installations using defaults and the following values:
Use ConTeXt binaries appropriate for OS:
ConTeXt version 2021.03.20 01:07. See questions at the end.

After an OS is installed, complete the following steps:
  1. Start VirtualBox
  2. Install ISO
  3. Log in as root
  4. Open a terminal
  5. Install wget
  6. Install gcc
  7. Install Guest Additions (to enable copy/paste between guest/host)
  8. Log in as username
  9. Open a terminal
  10. mkdir context
  11. cd context
  12. Download OS-specific ConTeXt binary
  13. unzip *zip
  14. sh
  15. Export PATH environment variable (OS-specific; see below)
  16. context --version
  17. mkdir -p ../tex
  18. cd ../tex
  19. Create "hello.tex": \starttext Hello \stoptext
  20. context hello.tex
  21. Stop VirtualBox
A hello.pdf file is created.

Build fails.

resolvers       > lua > loading file '/home/username/context/tex/texmf-context/tex/context/base/mkxl/spac-hor.lmt' succeeded
tex error       > tex error on line 25 in file spac-hor.mkxl: Undefined control sequence
<line 3.25> \bitwiseflip \normalizelinemode \flattendiscretionariescode
The control sequence at the end of the top line of your error message was never \def'ed. You can just continue as I'll forget about whatever was undefined.
mtx-context     | error, no format found with name: cont-en, aborting

Debian 10.8.0
Additional instructions:
Xubuntu 20.04.2
Additional instructions:
FreeBSD 12.2
Additional instructions:
Are there additional requirements that must be installed? If so, what are they and is there a way for ConTeXt itself to list them for the user?

Thank you!