Both are possible, but the first one is certainly much more common. (This may be more true in the US than in other places, since we tend to use past simple in the US even at times when past perfect would also make sense). Whether or not you can use the second one depends on the context, but I think you'll usually be safe with the first option.

Both are completely natural, but in different contexts. As Gray says, North Americans use the simple past much more than the British. So, to an American or Canadian, "I ended up" is completely natural and "I have ended up" sounds slightly odd. In my opinion, the simple past implies that the moment of "ending up learning" was at a known time, probably at the time of the story. Ex: When my nephew was 20, he was not a reliable worker. When the weather was good, he would skip work and go surfing at the beach. Sometimes, he would miss two or three days. After he got fired a few times for poor attendance, he ended up learning that going to work is required, not optional. The present perfect implies that the moment of "ending up learning" was at an unknown time, probably much later than the story. Ex: When my nephew was 20, he was not a reliable worker. When the weather was good, he would skip work and go surfing at the beach. Sometimes, he would miss two or three days. Every time that he got fired for poor attendance, he would always blame it on the boss not liking him. Now that he is older, he has ended up learning that going to work is required, not optional.

Thank you Chris!

Ignore James S-C. "I have ended up" is the present perfect and "I ended up" is the simple past.

Thank you James.