It may also help to practice strumming along with a video tutorial. YouTube is full of them. I like the Ukulele Fool, but there are many others. My first ukulele book was called 21 Songs in 6 Days (spoiler, it took me much longer than 6 days to work through the book). The first few songs in the book are songs that can be done with 1 chord, like “Row, Row, Row Your Boat “, which really allows you to focus on strumming (there are online videos that go with the book) because you know the words and aren’t changing chords.
Not saying get that book, just pick something dead easy that you know the lyrics to by heart and doesn’t have a lot of chord changes, and you’ll be able to focus on strumming evenly.