Thmyl Lbt Jyms Bwnd Llandrwyd Mn Mydya Fayr -

Try (A↔Z, B↔Y, etc.):

t (20) → g (7) h (8) → u (21) m (13) → z (26) y (25) → l (12) l (12) → y (25) thmyl lbt jyms bwnd llandrwyd mn mydya fayr

qejvi — nonsense.

y → i or e a → unchanged? f → f? r → r. So fayr = f a y r → f a i r = fair. Works. mydya = m y d y a → m e d i a = media. Works perfectly: y→e and y→i? That’s inconsistent unless y maps to both e and i — impossible for simple substitution unless one plaintext letter maps to two ciphertext letters (unlikely). Try (A↔Z, B↔Y, etc

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 . r → r