Thmyl Lbt Jyms Bwnd Llandrwyd Mn Mydya Fayr -

thmyl → gsnbo — no. Test shift of -3 (common in puzzles):

Try (A↔Z, B↔Y, etc.):

t→o, h→c, m→h, y→t, l→g → ocht g — no. Look at fayr → likely fair (y→i, common in archaic spelling). mydya → could be media (d→e? No). But mydya → if y=e, then medea (a name). llandrwyd — Welsh place name: Llandrwyd (real? Llandrwyd doesn’t exist, but Llanrwst, Llandrindod). Possibly llandrwyd → Llandrwyd as a proper noun. thmyl lbt jyms bwnd llandrwyd mn mydya fayr

Still nonsense. But note llandrwyd — Welsh has ll as a single phoneme, dd as voiced ‘th’, wy as ‘oo-ee’ sound. This suggests the plaintext might be Welsh or pseudo-Welsh . thmyl → gsnbo — no