Given the lack of clear decryption, but the phrase looks like it might be a playful scramble of a common phrase. One possibility: it's an accidental keyboard shift? Or simply nonsense.
"thmyl" → "lymht" "fylm" → "mlyf" "alans" → "snala" "walnms" → "smnlaw" "rb" → "br" "syd" → "dys" thmyl fylm alans walnms rb syd
That’s my creative output.
Alternatively, perhaps it's a Caesar cipher or Atbash. Trying Atbash (A↔Z, B↔Y, etc.): Given the lack of clear decryption, but the
"thmyl" → "mythl" (not a word) Maybe "thmyl" = "myth l" no. Given the lack of clear decryption
Still gibberish.
That gives "gsnbo" for first word — doesn't look promising.