Yes it was, as since it was never part of Roman empire it developed from missionary activity, and even started its own monastic missionary activity back to North Umbria, Faeroes and apparently even Iceland.
But was it doctrinally different from Chalcedonian Christianity to justify its own colour on the map. Wikipedia suggests no, which chimes with my understanding: some local minor differences in practice, but nothing like the Christological disputes that caused the rift with the Church of the East, nor like the row over papal supremacy etc. that led to the Great Schism between Roman Catholicism and Eastern Orthodoxy.
But was it doctrinally different from Chalcedonian Christianity to justify its own colour on the map. Wikipedia suggests no, which chimes with my understanding: some local minor differences in practice, but nothing like the Christological disputes that caused the rift with the Church of the East, nor like the row over papal supremacy etc. that led to the Great Schism between Roman Catholicism and Eastern Orthodoxy.