Install xchm chm viewer

 $ apt-cache search chm viewer
poppler-utils - PDF utilities (based on Poppler)
claws-mail-pdf-viewer - PDF and PostScript attachment viewer for Claws Mail
eog-plugin-send-by-mail - Send by Mail plugin for GNOME Image Viewer
kchmviewer - CHM viewer for KDE
ktnef - Viewer for mail attachments using TNEF format
libchm-bin - library for dealing with Microsoft CHM files (test programs)
libchm-dev - library for dealing with Microsoft CHM files (development)
libchm1 - library for dealing with Microsoft CHM files
okular-extra-backends - additional document format support for Okular
texlive-latex-extra - TeX Live: LaTeX additional packages
xchm - Compiled HTML Help (CHM) file viewer for X
x11-apps - X applications

 

:~$ sudo apt install xchm

Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
The following packages were automatically installed and are no longer required:
  linux-headers-6.11.0-19-generic linux-hwe-6.11-headers-6.11.0-19
  linux-hwe-6.11-tools-6.11.0-19 linux-image-6.11.0-19-generic
  linux-modules-6.11.0-19-generic linux-modules-extra-6.11.0-19-generic
  linux-tools-6.11.0-19-generic
Use 'sudo apt autoremove' to remove them.
The following additional packages will be installed:
  libchm1
The following NEW packages will be installed:
  libchm1 xchm
0 upgraded, 2 newly installed, 0 to remove and 5 not upgraded.
Need to get 232 kB of archives.
After this operation, 819 kB of additional disk space will be used.
Do you want to continue? [Y/n] y
Get:1 http://archive.ubuntu.com/ubuntu noble/universe amd64 libchm1 amd64 2:0.40a-8 [18.3 kB]
Get:2 http://archive.ubuntu.com/ubuntu noble/universe amd64 xchm amd64 2:1.36-1build2 [214 kB]
Fetched 232 kB in 4s (56.9 kB/s)
Selecting previously unselected package libchm1.
(Reading database ... 265890 files and directories currently installed.)
Preparing to unpack .../libchm1_2%3a0.40a-8_amd64.deb ...
Unpacking libchm1 (2:0.40a-8) ...
Selecting previously unselected package xchm.
Preparing to unpack .../xchm_2%3a1.36-1build2_amd64.deb ...
Unpacking xchm (2:1.36-1build2) ...
Setting up libchm1 (2:0.40a-8) ...
Setting up xchm (2:1.36-1build2) ...
Processing triggers for hicolor-icon-theme (0.17-2) ...
Processing triggers for gnome-menus (3.36.0-1.1ubuntu3) ...
Processing triggers for libc-bin (2.39-0ubuntu8.4) ...
Processing triggers for man-db (2.12.0-4build2) ...
Processing triggers for desktop-file-utils (0.27-2build1) ...