OK... deleted the whole Android SDK folder, extracted the 2 packages..... and I did now see 6609375 (win!) - but the original error popped up immediately ;-(
Ran the recommended updates (took a bit of time as it downloaded all the deleted tools, had to accept he license, etc.)
When trying to build, had these errors, so searched in the SDK Manager and added these:
Maven artifact not found: androidx.annotation/annotation-experimental
Maven artifact not found: androidx.viewpager2/viewpager2
Maven artifact not found: androidx.work/work-runtime
But still got this:
Maven artifact not found: com.google.guava/listenablefuture
I'll try the same thing again later, without running the updates and see whether that works (but as it immediately popped-up from the Libraries, something still not right).
Is this the right version?