I think I am repeating myself a little but I think it’s worth an examination in full.
I don’t think Russia will give too much of a Sh** for the following reasons:
1, JF 17 is an ok/good fighter for the money, but not state of the art. It is a match at best to older stuff the Russians would be fielding, except for maybe the AESA radar.
2, China will have all specs for the fighters, capabilities and limitations and most likely Russians will know it all, very thoroughly.
3, as the article describes Ukraine is cash strapped meaning that the likelihood of them doing major mods to the fighter is basically non existent, the military threat to Russia is minimal at best.
4, in terms of geopolitics Russia would want Ukraine being dependent on China than they would want Ukraine dependent and moving toward the West, tho at the moment Ukraine can’t afford it. If Ukraine buy Chinese, the West would be very wary of selling any hardware to Ukraine for fears of exposing their tech and possible reverse engineering. We should remember the aircraft carrier incident here too.
I think there is an argument to be had that Russia might even encourage China to sell the fighter to Ukraine, it would limit Ukraine’s military and political options at least until Ukraine’s economy is back on its feet, which let’s be honest here it would take a while.
During this time a Ukraine that is in China’s pocket would get no good will from the West and might in the long run bring it back into the sphere of influence of Russia, after China has extracted all that it wants.
Using your big brother, little brother analogy. The big brothers would be at the corner huddled up discussing, if an agreement is make, one big brother (Russia) will turn around, have a big smile with arms folded behind his back eyeing little brother (Ukraine), whilst the other big brother (China) will have a big smile walking to the little brother with shifty eye, both knowing that no matter what, the little brother have little options but to listen to them.