If Marvel didn't approve of Sony putting Venom in the MCU, they would have sued them for that post-credit scene or have forced them to remove that scene before the movie came out like what they did with the Tom Holland cameo in the first Venom movie. Marvel allowing that scene must mean there's plans for Venom in No Way Home.
Don't expect Feige to say that the Venom post-credit scene is "not canon" (regardless of whether or not he agrees with Sony having a hand in the canon). They have a new deal with Sony, they're on good terms.
