457 Answer Book (Wolters Kluwer 8th ed. & Supp.) is updated for the laws you mention. Or call me.
In early January, I revised my governmental § 457(b) clients’ plans to follow the “Setting Every Community Up for Retirement Enhancement Act of 2019”, the “Bipartisan American Miners Act of 2019”, and the “Taxpayer Certainty and Disaster Tax Relief Act of 2019”.
Also, I then added a provision for future disasters, and it was enough to provide the Coronavirus Aid, Relief, and Economic Security Act’s coronavirus loans and distributions without touching the document again.
The Bipartisan Budget Act of 2018’s addition to § 401(k) about hardship distributions does not affect, at least not directly, § 457(b)’s tolerance for an unforeseeable emergency.
Section 457(b) does not have its own “remedial amendment” regime. Yet, the recent statutes might allow some delay for a governmental plan. But don’t assume everything is under SECURE’s remedial-amendment date; some provisions are under other divisions of the Further Consolidated Appropriations Act, 2020.
For a governmental plan, a State’s law often requires a written plan’s revision much sooner than Federal tax law requires.