I'd braze it with nickel-silver, which is stronger than brass ('bronze") brazing filler, about the strength of some steels in fact. Slightly hotter melting than brass, but not a problem. I made one lugless frame, 531 tubes, completely brazed with nickel-silver in the '70s, and that frame was still being ridden last I heard, maybe 10-15 years ago (maybe still is). I don't actually recommend fillet-brazing with nickel-silver, but it has proven reliable if you want to. But it is excellent for repairs.
Semi-retired framebuilder and YouTuber
Paul Brodie likes it, uses it a lot including for fillet-brazed frames, though he only makes a small braze with nickel-silver, and then he builds up the fillet with brass. Nickel-silver is difficult to file and smooth, more chance to accidentally thin the steel wall thickness, so brass is safer in that way, but nickel-silver allows you to make smaller fillets. If you don't file them at all, then that makes it a good choice. Of course for this repair, you won't be filing anywhere near the tube, only on the lug, so 100% safe.
For those who don't know, nickel-silver is a misnomer since it contains zero silver. I think the name comes from it being sorta silver-colored. It's actually a cousin of brass, containing mostly copper and zinc, but with a substantial amount of nickel which adds strength. You can use it with the same flux you use for brass, but I recommend the flux
Cycle Designs makes specifically for nickel-silver. You can buy the rod from them too, or there are other makers. The stuff I used in the '70s was All-State #11. It comes as bare or flux-coated rod; I always use the bare rod, with paste flux. Flux-coated might be useful for a repair like this, but I haven't tried it.
Mark B