Credit goes to Frith for pointing out how magic-E on ⟨u⟩ used to make the native long-U sound.
Credit goes to ShrekBeeBensonDCLXVI on the Anglish Reddit for sharing the idea that ⟨tch⟩ was invented to distinguish the new French pronunciation of ⟨ch⟩ from the old one.
Credit goes to Henry Bane of Calques of the Anglish Discord for pointing out that the loss of ⟨hr⟩ and ⟨hl⟩ could have influenced the switch from ⟨hw⟩ to ⟨wh⟩.
Credit goes to Eadwine of the Old English Discord for pointing out that replacing ⟨ie⟩ with ⟨ea⟩ rather than ⟨ee⟩ is not supported with evidence as far as we can tell.
Credit goes to Yose of the Anglish Discord: for pointing out that ⟨th⟩ was rising in popularity in the decades before the printing press; for pointing out that Iceland was able to procure printing blocks for ⟨þ⟩, showing that Englishmen could have as well if they wanted to; for pointing out for ⟨e⟩ in words like ceosan would likely have been retained had ⟨ch⟩ never been borrowed, since ⟨e⟩ in such words would be helpful for indicating the sound of ⟨c⟩.
Credit goes to the YouTube channel "Middle-English Manuscripts" for helping me find the Anglo-Saxon charters which contain ⟨u⟩ making /v/.
Credit goes to Andwlite of the Anglish Discord for finding sources on the ⟨o⟩ to ⟨u⟩ switch, and for alerting me to the ⟨y⟩ to ⟨u⟩ thing.