You can _definitely_ learn enough garage band to make a simple loop! It's very easy to set up, actually - at least on desktop, and I'm sure it's similar enough on the mobile app.
You can mark a section on the timeline to loop, and if you record when you're in that state, it'll just continually record to that same section of track. You can also set it up to do a metronome count in before actually recording. So, if you can manage to stay on time for 2 or 4 bars in one go, you can just record some quarter note strums into your phone mic - bang, perfectly serviceable loop for practice.
You can even start out with just a loop of a single chord to get a sense for how different notes sound against it in context. When that gets boring, do a little I-V or I-IV loop and try to notice the change in feel of different notes in, say, the major pentatonic scale for the root note. Then try a twelve bar blues, and then, ya know, whatever. It's a lot of fun, I'll often just toss out a quick loop and noodle if I've got ten minutes between meetings or a long build or something.
You can mark a section on the timeline to loop, and if you record when you're in that state, it'll just continually record to that same section of track. You can also set it up to do a metronome count in before actually recording. So, if you can manage to stay on time for 2 or 4 bars in one go, you can just record some quarter note strums into your phone mic - bang, perfectly serviceable loop for practice.
You can even start out with just a loop of a single chord to get a sense for how different notes sound against it in context. When that gets boring, do a little I-V or I-IV loop and try to notice the change in feel of different notes in, say, the major pentatonic scale for the root note. Then try a twelve bar blues, and then, ya know, whatever. It's a lot of fun, I'll often just toss out a quick loop and noodle if I've got ten minutes between meetings or a long build or something.