MuseScore is a phenominal free music notation app. Useful in so many ways, whether you are writing your own music, or learning someone else's. Note that this link takes you to MuseScore.org, where the free app resides, and not to MuseScore.com, which requires a subscription to view other composer's arrangements.
If you're going to be learning music theory, you'll want a keyboard close at hand. If you don't have your own piano, there are fortunately a number of free virtual pianos online. This is one that I've found useful.
There's tons of good stuff at MusicTheory.net, including free Lessons, Exercises, and Tools. There's enough here to keep you busy for a very long time.
The Toned Ear has many excellent exercises for developing your musical ear.
If you're looking for a book of period songs for the ukulele, From Lute to Uke, by Tony Mizen, is likely one of the first you'll run across. It includes 24 pieces of period lute music arranged for ukulele, with both tablature and standard notation. Although this book is arranged with the simplest songs at the start, beginners are likely to find most of the material quite challenging.
One of my favorite sites! This one gives you a random (but great sounding) chord progression, along with fingering charts for all the chords needed. There's no sound, so you can play at your own speed, and experiment with different strum patterns. If the chord progression looks too challenging, just hit the "Give Me Another" button at the bottom until you find one that fits your capabilities.
Here's a PDF e-book available for purchase, that includes the first 15 pieces from Tielman Susato's "Danserye", arranged for solo ukulele by Wilfried Welti. There are also videos of several of the songs. The arrangements are lovely, and suitable for an intermediate level player.
Also from Wilfried Welti, this PDF e-book includes 16 rondes and bransles from Tielman Susato's "Danserye", arranged for solo ukulele. Just like his first book, these are lovely arrangements which are suitable for an intermediate level player. Check out the videos of him playing some of the songs.
Helmut Bickel is one of my favorite people on YouTube. He has put together literally hundreds of arrangements for both guitar and ukulele, and then created video tutorials for them. Most of them are not SCA appropriate, but a surprising number of them are, including some period songs, along with folk songs and other traditional pieces.
Friday Night Bardic is the brainchild of Master William Brewer, who began hosting virtual bardic circles in the early days of the pandemic. Hosting duties are currently being shared by THL Davock Walkere and THL Rohais de Ravenscroft. Come join us on Zoom! We're here every Friday, starting at 8:30 pm eastern. Joining the Facebook group is also a great way to hear about virtual bardics being held by other groups.