AnyDesk was updated to the latest version that supports CentOS 7 (EOL OS)

First the YUM repositories were migrated, as the original address was offline due to EOL

# mv yum.repos.d yum.repos.d_old
# git clone https://github.com/tkne/centos-7-repo.git yum.repos.d

The OS was updated and a needed package was installed:

# yum update-minimal
# yum install gtkglext-libs

Finally AnyDesk was downloaded:

# https_proxy=http://proxy.gsi.de:3128 wget https://download.anydesk.com/linux/anydesk-6.3.3-1.el7.x86_64.rpm
# yum install anydesk-6.3.3-1.el7.x86_64.rpm

Note that later versions (such anydesk 6.4 or 7.0) refuse to install as CentOS 7 has too old a GLIBC
The only "fix" I observe is upgrading to a supported edition such as AlmaLinux (as used by CERN)
This would need to be coordinated with STFC