Can you give us an idea of how often platform changes occur at a comparably busy Finnish terminal station and how passengers are advised - displays, announcements, text alerts, staff presence or whatever? Thanks.
Helsinki's central station, the country's intercity hub, has 19 platforms, an intensive commuter service and 45 million passengers/year (with virtually no interchanges). Firstly, it has three platform areas: the east (1-4) and west (13-19) side platforms for their repective commuter services and the central, longer platforms (5-12), used for long-distance services. Services virtually always stay in the same platform group.
Platforms are never changed without good reason - usually because the incoming train is late (or the outgoing hasn't left yet!) and it gets diverted into the designated contingency platform (4 for the east side, used for a hot spare off-peak, 11 for the centre and 13 for the west side). When they are, the new platform number is highlighted red on all displays. In addition, it's shown on the old platform's boards so if you turn up there, you know where to go. An announcement is made in Finnish, Swedish and English ("InterCity 178 to Tampere leaves exceptionally from track 11") not long after the platform is changed (usually 20-30 minutes out). If you've booked a ticket on the VR app, it'll send you a notification letting you know in no uncertain terms where to go.
One stop up the line at Pasila, 5 minutes out from Helsinki, where every service stops, the main route has a pair of island platforms for the faster commuter and intercity services. Intercity services are often held here for connections (or break down!) from the other route (there's a Y-style junction just south): this allows them to divert around that without inconveniencing passengers. Pasila has 460,000 interchanges/year and 17.9 million entries/exits. There are no fewer than three completely different ways to change between the 10 platforms.
I should add that there are no ticket barriers in Finland and you can walk onto the platforms from the surrounding streets in umpteen different places. Platforms are never supressed (and sometimes displayed up to 12 hours before!) and you're always allowed on as soon as the train rolls in from the depot or from its previous working.
All the passenger stats are from 2019.