ResearchBitcoin Dev Archive BIPs
BIP 379: Miniscript
Applications, Specification, Draft. By Pieter Wuille, Andrew Poelstra, Sanket Kanjalkar, Antoine Poinsot, Ava Chow. Never named in a subject line or discussed by number on the list.
In Bitcoin Core
First shipped in Bitcoin Core 24.0 (also touched in 26.0).
Miniscript was partially implemented in v24.0 (PR 24148), and fully implemented as of v26.0 (PR 27255).
From Bitcoin Core's doc/bips.md.
The threads, in order
No thread on the list names this BIP. Search the archive for its title if you think one should.