Bitcoin Optech's annual year-in-review: https://bitcoinops.org/en/newsletters/2020/12/23/

Covers taproot, tapscript, schnorr, DLCs, LN large channels, LN dual/interactive funding, LN blinded paths, exfiltration resistant signing, payjoin, PTLCs, BIP85 keychains, vaults, tx origin privacy improvements, SAS, coinswap, compact block filters, various attacks and weaknesses, wabisabi, wtxid tx relay, signet, anchor outputs, faster sig verification, COPA, generic signmessage, musig2, v2 addr, LN Pool, LN offers, and more.