I’m the main developer of a library which package is on conda-forge since a few years.
However, years ago, before using the conda-forge channel, some package versions have been uploaded on the main conda channel.
The issue is that some new users, who do not pay attention to the installation instructions, are installing the package via conda install XXX instead of conda install -c conda-forge XXX, and are installing obsolete versions (and complaining that stuff are not working
Is there any way to suppress the packages that are not on the conda-forge channel?
If you mean about the packages on defaults (aka Anaconda’s pkgs/main), they are maintained at Anaconda Inc - Anaconda Recipes · GitHub (use the Github search to find the recipe for your package).
That said, the conda promise is that the packages are always available for long term reproducibility, so maybe your best bet is to try to reach out and get your package updated in the Anaconda repo.