The only way to fix it safely would be to dissolve the epoxy, remove the lug from the tubes, and either replace with a new lug or do a TIG weld repair on the crack, which would involve welding with aluminum filler rod, heat treating, and then sanding and polishing down to the original profile and finish. Then the lug would need to be re-epoxied back onto the tubes in an appropriate fixture. Unless you're willing to spend thousands of dollars on this repair, it's not going to happen. You can't just bring this to your local framebuilder to have repaired. Most framebuilders do not weld aluminum, and do not work with epoxy construction. Even if you approached a seasoned aluminum framebuilder like Ventana or FTW, I doubt they would take the project on as it involves a glued frame.
It's just a bike. There are others that will ride just as well. Hang it up and start a new project.
Last edited by TenGrainBread; 07-11-19 at 10:09 AM.