This is almost identical to my setup and I get a single copy everywhere. Intervals.icu is smart enough to discover that the workout on Strava is the same one that it got from Rowsandall. The sync with Concept2 runs every few minutes. Please check, or otherwise do a manual import (whichI I do) and let me know.
I fear I have a problem, on logbook concept the activity is present almost immediately, while on both Intervals and Strava it still does not appear
Can you see it on Rowsandall Rowing Data Analytics and then import it?
The link Rowsandall Rowing Data Analytics takes you directly to the manual import from C2 Logbook.