I fitted Givi bars on my 2018 Euro 4 a couple of months ago and I didn't touch the rear brake reservoir, didn't use the supplied extender bracket. I offered it up, it looked like it wasn't going to foul the bars, fitted the bars and I have clearance, not a lot but enough to get a slice of British Rail ham in there. I was prepared to uncrew it all if it did foul, but it didn't. Ditto a French geezer with a 2021 model on YT whose vid I watched who also mentioned the hose is too short so you may be lucky. Give it a whirl.