Sybok is not canon.
"But CBS says it's all canon"
CBS are a giant corporation that basically say everything is canon because they want fan money. Lets be real, TAS is not canon, and several of the movies are not canon, especially Star Trek V.
Roddenberry did not consider STV or TAS canon so when Star Trek came back to TV with TNG, TAS and films like STV were completely and totally ignored and basically retconned out of existence by the writers. Sarek never in TNG when dealing with his family mentions Sybok, so it's clear the writers went with Roddenberry's vision that Sybok and STV is not canon. Just like in TAS the Holodeck exists, but is brand new technology in TNG.
I've always hated the "CBS says it's canon so it's canon" nonsense, no, that's horse crap, CBS do not make Star Trek, They're just a bunch of suits who probably don't even know anything about Star Trek beyond the $$$, the writers do and the writers and CREATOR of Star Trek did not consider this shit canon, so it's not canon. TNG further confirms this with Sarek never, ever mentioning Sybok despite the story line in TNG would have most likely involved Sybok as well if he actually existed.
On Burnham, the problem with Burnham is that she was written by a 14 year old over at fanfiction.net and gave her the dumbest Mary-Sue backstory in Star Trek. The "Sister of Spock" stuff is complete and utter eye rolling nonsense and again, completely contradicts Sareks storyline in TNG. But, it's canon, it doesn't fit in well and it shows what hacks the writers are, but it's canon so how will it be resolved? I suspect the writers just hope you never question it.