Initial keyboard setup does not work

Indeed I had the same issue, try having ~/.dhexrc
#DHEXCOLORSCHEME
#VERSION 0
#possible colors are: BLACK,RED,GREEN,YELLOW,BLUE,MAGENTA,CYAN,WHITE
#possible extra flags are: UNDERLINE,REVERSE,BLINK,DIM,BOLD
BRACKETS: FG=BLACK,BG=BLACK,BOLD
HEXFIELD: FG=WHITE,BG=BLACK
INPUT: FG=BLACK,BG=WHITE
CURSOR: FG=WHITE,BG=BLACK
TEXT: FG=WHITE,BG=BLACK,BOLD
MENU_NORMAL: FG=CYAN,BG=BLACK
MENU_HIGHLIGHT: FG=BLACK,BG=CYAN
MENU_HOTKEY: FG=YELLOW,BG=BLACK,BOLD
MENU_HOTKEY_HI: FG=YELLOW,BG=CYAN,BOLD
FRAME: FG=BLUE,BG=BLACK,BOLD
NORMAL_DIFF: FG=YELLOW,BG=BLACK
CURSOR_DIFF: FG=YELLOW,BG=WHITE,BOLD
HEADLINE: FG=BLUE,BG=BLACK,BOLD
HEADER: FG=BLACK,BG=CYAN
KEYF1:1b 5b 31 31 7e
KEYF2:1b 5b 31 32 7e
KEYF3:1b 5b 31 33 7e
KEYF4:1b 5b 31 34 7e
KEYF5:1b 5b 31 35 7e
KEYF6:1b 5b 31 37 7e
KEYF7:1b 5b 31 38 7e
KEYF8:1b 5b 31 39 7e
KEYF9:1b 5b 32 30 7e
KEYF10:1b 5b 32 31 7e
KEYESC:1b
KEYBACKSPACE:08
KEYDEL:7f
KEYENTER:0a
KEYTAB:09
KEYUP:1b 5b 41
KEYDOWN:1b 5b 42
KEYRIGHT:1b 5b 43
KEYLEFT:1b 5b 44
KEYPGUP:1b 5b 35 7e
KEYPGDOWN:1b 5b 36 7e
KEYHOME:1b 5b 37 7e
KEYEND:1b 5b 38 7e

from its manual page

I belive this is caused by a high cpuload patch in 0.69

This bug was fixed in the package dhex - 0.69-2

---------------
dhex (0.69-2) unstable; urgency=medium

  * New maintainer. (Closes: #973686)
  * Using new DH level format. Consequently:
      - debian/compat: removed.
      - debian/control: changed from 'debhelper' to 'debhelper-compat' in
        Build-Depends field and bumped level to 13.
  * debian/control:
      - Added Rules-Requires-Root: no.
      - Added Vcs-* fields in source stanza.
      - Bumped Standards-Version to 4.5.0.
      - Changed Homepage field to use a secure URI.
  * debian/copyright:
      - Added myself and Axel Beckert to packaging block.
      - Added Upstream-Contact field.
      - Updated years in packaging block.
      - Using a secure URI in Format and Source fields.
  * debian/patches/:
      - 010_fix-typos.patch: added to fix several typos and spelling errors.
      - 020_hardening-fix.patch: added to be possible to implement hardening.
      - cpu-load: removed, does not work with 0.69 and causes buggy behavior.
        (Closes: #940536, LP: #1814478)
      - fix-typos: removed, was replaced by 010_fix-typos.patch.
      - harden: removed, it doesn't work in 0.69.
      - series: updated to reflect the changes.
  * debian/rules:
      - Removed unnecessary DEB_LDFLAGS_MAINT_APPEND flags.
      - Removed unnecessary DEB_CFLAGS_MAINT_APPEND flags.
  * debian/salsa-ci.yml: added to provide CI tests for Salsa.
  * debian/tests/:
      - control: created to perform a trivial CI test.
      - files/sample.txt: added to be used on tests.
  * debian/upstream/metadata: created.
  * debian/watch:
      - Bumped to version 4.
      - Updated to use a secure URI with HTTPS protocol.

 -- Fabio Augusto De Muzio Tobich <email address hidden> Mon, 09 Nov 2020 13:06:23 -0300

I can reproduce this bug exactly as described above in up-to-date 20.04 Focal Fossa. The fix has been applied to Hirsute, and Impish, but not Bionic or Focal. Would it be possible to backport the fix, please? The dhex package is broken (always freezes on startup) without it.

An easy workaround for Ubuntu 20.04 is to use the version from 21.10:

wget http://mirrors.kernel.org/ubuntu/pool/universe/d/dhex/dhex_0.69-3_amd64.deb
sudo dpkg -i dhex_0.69-3_amd64.deb

http://mirrors.kernel.org/ubuntu/pool/universe/d/dhex/dhex_0.69-3_amd64.deb

No longer exists.

So I tried:
dhex_0.69-4_amd64.deb

which errors out with:

dpkg: dependency problems prevent configuration of dhex:
 dhex depends on libc6 (>= 2.34); however:
  Version of libc6:amd64 on system is 2.31-0ubuntu9.9.

Your C library is too old what Ubuntu version do you run?