I am running into this problem as well when trying to install qiime2-amplicon-2024.5 on our HPC running CentOS-7, running conda 24.9.2. Sadly none of the suggested work arounds are helping. I was able to install c-ares, but installing glibc has been an issue. I've even tried installing glibc several different ways w/o success. I keep getting this error:
Could not solve for environment specs
The following package could not be installed
└─ c-ares 1.33.1** is not installable because it requires
└─ __glibc >=2.28,<3.0.a0 , which is missing on the system.
I should note that I did not have this issue when qiime2-amplicon-2024.5 was first released. I was able to install it just fine. Now, for whatever reason, I am unable to do so.