here it says it was 1.4m:
https://psgtalk.com/2019/10/veronique-rabiots-modest-commission-after-adriens-transfer/
but they say 3.6 for Ramsey, which was reported by Juve in official statement, while nothing was reported for Rabiot, which probably means there was nothing.
edit: sorry it also state he received 10 mil, 1.4m is just agent, still its strange because Juve reported the signing on fee for every player, but i cant find anything on him.