I want to know the answer to the following question:
When eth is replaced, what is it replaced by?
All the background I'm provided with is that "The modern forms of Latin letters are used, including ⟨g⟩ in place of the insular G, ⟨s⟩ for long S, and others which may differ considerably from the insular script, notably ⟨e⟩, ⟨f⟩ and ⟨r⟩. Macrons are used to indicate long vowels, where usually no distinction was made between long and short vowels in the originals.". Is that enough to answer the question?
Answer: no