Here's my experience:
- iPhone Xs Max on AT&T
- Located in NYC
- Activated in Apple store with new SIM
- Set up from an iCloud backup
- Horrid LTE speeds ~1-3mbps (via Ookla Speedtest)
- Horrid WiFi speeds ~10mbps (via Ookla Speedtest)
- Tried resetting network settings; airplane mode on/off; power on/off
- Opened Apple Support ticket on their forums
- Went to Genius Bar - was told this was a developing issue they are hearing more about and to wait for news/update from Apple
- Today I received a call from Apple support in response to my ticket and forum post asking me to send logs; this will be hard for me given work and availability
- The ONLY time I have gotten normal WiFi speeds (~150-200mbps) has been at the office
- I work in a financial institution and have no info on their equipment or settings