One thing for sure, any beginner reading this thread will be scared away.
I had some music theory in high school, and went through the different kind of scales and how the same chord progressions sounds good on different keys and are used over and over. I wasnt profissient on any instrument, so didnt quite put the scales to use though.
Anyway, I have forgotten almost everything about scales. Besides how the basic ones are colour coded for C/Am on a piano and perhaps finding the "blues scale" in one key on piano. And I dont refer to chord progressions on the abstract way with numbers, dont think about it usually.
It is good to know that they exist, but there is no need to know it all by heart.
I would recommend any beginner to go trough some very basic music theory, there must be a video on youtube that is better than nothing, and see what they can use. Perhaps not as the first thing they do, but after strumming the first couple of songs.
And if you want to sing with your uke I would recommend learning how to dechifer staff notation. I say dechifer, not play from. Just to understand it, so if there is a note in the melody you are in doubt of, you can look it up. And very important, if you determine your vocal range you can see if the song is in the right key for you. Yes, I know that some people are musical enough to just hear that, but I am not.
You all write about phrygian scales and how you might need to correct the music sheets because you should know better than the person who wrote it. I think this is not the first thing for a beginner to worry about.