John Meade surveys ch. 4 of Ronald Hendel and Jan Joosten’s How Old Is the Hebrew Bible? (YUP, 2018) and promises a follow-up post “attempting to engage the authors on one of their examples from chapter 4 with a view to showing how they think diachony and TC work together.”
The Vatican Library has made available a digital facsimile of Codex Marchalianus (7th–8th c.). The codex contains some prefatory material and the text of the prophets, including Baruch and the Letter of Jeremiah. Each page has two scans with alternate lighting. Below is a sample of the marginalia from Isa 25:8 (leaf 231) that notes the alternate readings for the passage in Theodotion (top) and Aquila (bottom).