I think warrant canaries might offer reassurance only if the jurisdiction is permissive with warrant canaries. There are jurisdictions that essentially criminalize warrant canaries, whether by making it a crime to disclose the absence of legal instruments (either in general or certain instruments) or by construing the removal of a warrant canary as a disclosure that something was served (lying would be compelled in this case).
Alternative to warrant canaries is service providers that are unable to disclose sensitive information because of technology baked into the service they provide prevents them from doing so. Not logging helps too. IIRC, when Signal could only turn over trivial data when they were subpoenaed, and some internet services accept only Tor traffic.