At the https://common-lisp.net/project/cl-stm/
there is a link "Browse the latest source code".
It refers to https://common-lisp.net/cgi-bin/darcsweb/darcsweb.cgi?r=cl-stm-cl-stm%3ba=summary
As I understand, darcs repos were migrated to GitLab.
Maybe it makes sense to map the old URLs to the corresponding GitLab URls?
Best regards,
- Anton