OP here.

I've seen much recent discussion on HN about robocalls not being resolved by the new STIR/SHAKEN protocol arising from the TRACED Act. I found this on https://regulations.gov and thought it would be of interest.

The big US providers have implemented the STIR/SHAKEN caller ID authentication framework as of mid-2021 but there was a 2-year extension to mid-2023 for small providers. The implementation appears to have been ineffective at stopping robocalls because of origination via the exempt small providers. The FCC has now passed a rule that a subset of small providers (those most likely to be originating illegal robocalls) must be in compliance by mid-2022.

TLDR - if this works there should finally be a dropoff in robocalls this summer.