Comment 1 for bug 1798089

The RAR licence is "non-Free".

21.04/Hirsute has libclamunrar and libclamunrar9 (I think in the "non-free" packages):

I note that these are version 0.102.3-3
which is older than my clamav 0.103.2+dfsg-ubuntu0.21.04.1

# apt show libclamunrar
Package: libclamunrar
Version: 0.102.3-3
Priority: optional
Section: multiverse/libs
Origin: Ubuntu
Maintainer: Ubuntu Developers <email address hidden>
Original-Maintainer: ClamAV Team <email address hidden>
Bugs: https://bugs.launchpad.net/ubuntu/+filebug
Installed-Size: 20.5 kB
Depends: libclamunrar9
Homepage: https://www.clamav.net/
Download-Size: 4,972 B
APT-Manual-Installed: yes
APT-Sources: http://gb.archive.ubuntu.com/ubuntu hirsute/multiverse amd64 Packages
Description: anti-virus utility for Unix - unrar support
 Clam AntiVirus is an anti-virus toolkit for Unix. The main purpose of this
 software is the integration with mail servers (attachment scanning). The
 package provides a flexible and scalable multi-threaded daemon in the
 clamav-daemon package, a command-line scanner in the clamav package, and a
 tool for automatic updating via the Internet in the clamav-freshclam
 package. The programs are based on libclamav9, which can be used by other
 software.
 .
 This metapackage depends on the current libclamunrarX binary library to
 ensure a new libclamunrarY will be installed after a soname update.

Package: libclamunrar9
Version: 0.102.3-3
Priority: optional
Section: multiverse/libs
Source: libclamunrar
Origin: Ubuntu
Maintainer: Ubuntu Developers <email address hidden>
Original-Maintainer: ClamAV Team <email address hidden>
Bugs: https://bugs.launchpad.net/ubuntu/+filebug
Installed-Size: 311 kB
Depends: libclamav9, libc6 (>= 2.14), libgcc-s1 (>= 3.0), libstdc++6 (>= 5)
Homepage: https://www.clamav.net/
Download-Size: 121 kB
APT-Manual-Installed: yes
APT-Sources: http://gb.archive.ubuntu.com/ubuntu hirsute/multiverse amd64 Packages
Description: anti-virus utility for Unix - unrar support
 Clam AntiVirus is an anti-virus toolkit for Unix. The main purpose of this
 software is the integration with mail servers (attachment scanning). The
 package provides a flexible and scalable multi-threaded daemon in the
 clamav-daemon package, a command-line scanner in the clamav package, and a
 tool for automatic updating via the Internet in the clamav-freshclam
 package. The programs are based on libclamav9, which can be used by other
 software.
 .
 This package provides support for RAR packaged files or mail attachments.
 Support will be available once this package is installed and clamd or a
 local clamscan is restarted.