Can't be long till details are released as Millwall have published their ticket details:
https://www.millwallfc.co.uk/news/2019/february/tickets--millwall-v-brighton--hove-albion/
That is the current criteria.
Here is a link to the initial on sale dates:
https://www.brightonandhovealbion.com/news/2019/january/palace-tickets-on-sale-tuesday/