Two more umbrella struts snapped and required the same repair, but, having drained all the suitable snippets from the Box o’ Brass Cutoffs, some lathe work was in order:

I used the carbide insert in the mistaken belief it’d be less grabby, then applied the cutoff tool.
Break the edges, slide splints over the ribs, slobber epoxy on the struts, slide splints into place, apply masking tape for a bit of compression & alignment, and let it cure:

Three down, five to go …