Thanks for your post.
While this cannot be completely disabled, you do have the ability to disable the push notification. Push notifications are "pushed" to your mobile device when the Strava app is either closed or running in the background.
This can be turned off by going to:
Settings (top right)
Un-toggling Device Activity Synced
The push notification settings do not affect the in-app notifications you receive in the mobile app or on the Strava website.
We also have an existing thread where we are collecting feedback on this topic, I can see you have already added your comment there also, thanks for doing that. We appreciate you taking the time to share your feedback.