For RockyLinux 9 run the following as root:
cd /etc/yum.repos.d/
wget https://download.opensuse.org/repositories/home:indimail/RockyLinux_9/home:indimail.repo
yum install libidn
For RHEL 7 run the following as root:
cd /etc/yum.repos.d/
wget https://download.opensuse.org/repositories/home:indimail/RHEL_7/home:indimail.repo
yum install libidn
For AlmaLinux 9 run the following as root:
cd /etc/yum.repos.d/
wget https://download.opensuse.org/repositories/home:indimail/AlmaLinux_9/home:indimail.repo
yum install libidn
For AlmaLinux 8 run the following as root:
cd /etc/yum.repos.d/
wget https://download.opensuse.org/repositories/home:indimail/AlmaLinux_8/home:indimail.repo
yum install libidn