Europeans colonized almost the entire planet but never established colonies in Europe itself. For example, no one colonized France or Germany despite having been conquered several times.
Why was there no intra-European colonialism?
this answer by u/Itsalrightwithme on the difference in how the early modern Spanish kings ruled their Dutch subjects and their subjects in Latin America might give some insight.
I wonder if u/Rimbaud82 gets tired of me pinging their answers on these questions.
Digressions aside, Ireland was England’s first adventure at colonialism. Here’s a detailed answer under Would we say that England "colonized" Ireland? How was it similar to/different from colonialism in other parts of the world?
Or a more recent answer under why only the northern part of ireland colonised and not the entire country?