It is not possible to change hostname for AlmaLinux TDN template in SolusVM.
KVM template file names should have certain format
kernel-os-os_version-arch-custom_name-gen-version.gz. SolusVM parses template file name and decides what features are applicable to VPS created from the template. AlmaLinux is not in the list of supported OSes.
The feature request for AlmaLinux support with #SVM-3198 has been submitted and considered to be included in future releases
As a workaround, rename template file name as below:
# cp -a /home/solusvm/kvm/template/linux-almalinux-8-x86_64-gen2-v1.gz /home/solusvm/kvm/template/linux-centos-8-x86_64-almalinux-gen2-v1.gz