The package manager doesn’t show it anymore.
Recently they made some changes to the "modx.com"
package provider. I could be, that the package was (maybe accidentally) removed during this process.
Looking at github, this extra hasn’t been changed in a decade.
You could load the transport package from github and install it manually.
Or maybe it’s time to switch to an extra that is better maintained (like GoogleSiteMap or SEOSuite).
It appears the owner of that extra, with username “robodesign”, is not in the user system. As a result, that extra was not migrated to the new database. I will attempt to find a way to resolve this and report back.
If you are looking for an alternative, there is pdoSitemap inside the pdoTools extra. SEO Suite has also a Sitemap feature but this extra is more “intrusive” as it adds custom fields to all resources and additional SEO fields…
Yes, I tried the other siteMap Extra’s and I do use them in other projects, but sitemapFriend suited best in this one.
I switched to pdoSitemap finally, just had to set &scheme=full
to make it work the same way as sitemapFriend