instead off adding mdbook-linkcheck, skip it since there isn't much use for us
diff --git a/doc/manual/book.toml.in b/doc/manual/book.toml.in
index 34acf642e..07c09da37 100644
--- a/doc/manual/book.toml.in
+++ b/doc/manual/book.toml.in
@@ -27,6 +27,7 @@ command = "jq --from-file ./anchors.jq"
 [output.linkcheck]
 # no Internet during the build (in the sandbox)
 follow-web-links = false
+optional = true

 # mdbook-linkcheck does not understand [foo]{#bar} style links, resulting in
 # excessive "Potential incomplete link" warnings. No other kind of warning was