Sure, they do. Only British trains do not run.

However times might not be published yet after the yearly timetable change on 15th December. Just wait a bit.

You can check the current timetables, they won't change much. The most straightforward route is 3 ICs via Antwerp and Gent.

Reservations are not possible on Dutch & Belgian domestic trains + hourly cross-border IC. Hop on and sit wherever you want, the train ends are usually less busy.

Only exception would be Eurostar but the 27€ fee is way too high + you lose all flexibility.

Trains are running, just hop on at any Intercity service to Antwerp and Brugge. No worries and no reservations needed.