The winger, who has been involved in the academy setups at Swansea City and Hull City, will link up with the Bluebirds on a one-year deal.
Dyer, 19, made 12 appearances in the JD Cymru South last season, providing four assists as the Neath Port Talbot side secured a third place finish.
The youngster has also represented Wales at age grade level, having made his debut for the under-18s against England in Cardiff back in 2021.
His name is Rio and he plays for Haverfordwest!
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