You might want to check if access to the platform by elevator is possible
Belgian trains in theory have bike compartments.
Since some of the trains are very long and the conductors sometimes need to have to open up the compartments you might still end up transporting your bike in a different way.
see https://www.eurostar.com/rw-en/travel-info/travel-planning/luggage/bikes you need to make a reservation for your bikes with Eurodispatch and then bring your bikes to the luggage counter and pick them up at the other end of your connection. E.g. going from Brussels to London you bring your bikes to the counter at Brussels Midi (see pictures) below and pick them up at London St. Pancras International.
The EuroDispatch counter is at the far end past the baggage storag counter.
Some german regional trains have bike compartments with plenty of space for bikes. No reservation is required. On some routes that are favored by bicyclist the spaces might be used up in summer especially on weekends.