This may sound strange but I learn very well using true/false questions. I feel that they really test my understanding of theorems/properties. I also find them quite fun to do.
However, I'm having a very rough time finding them.
Do you know of any books or any sources that contain a good number of these, so that I may test my understanding?
I found this in one of the other posts. This is precisely the kind of thing that I am looking for.
As hinted by Gerry in the comments, A First Course in Abstract Algebra by John B. Fraleigh contains some true-false end-of-chapter questions.
There are also the following MSE posts about true-false questions for abstract algebra:
five true or false questions on abstract algebra
True or false question about polynomial ring
True/False about ring and integral domain
Abstract algebra true or false answer check
(Theoretical Questions) Determine the following statements are true or false.
I also found the following True or False Quizlets from Joseph Gallian's course webpage for Math5371 at University of Minnesota Duluth.