I'm spitballing different ideas I've used:

• Like you said, talk to people who know the topic and find it interesting.

• Read non technical introductory books on the topic. I found the algorithmn's part of CS interesting, but the EE dimensions of computing was utterly boring until I read Code by Charles Petzold.

• Research the history of a topic in order to see the lives of the humans who worked on it. Humans being social creatures, may find a topic more interesting after they have learned of some of the more interesting people who have worked in that field.