Similar experience with the following setup:
- iMac (M1)
- 2 LG UltraFine Monitors
- Belkin TB3 Dock Pro
- StarTech USBC to DP1.2 Cable & Adapter
- macOS Sonoma 14.2.1
- DisplayLink 1.11 (also tried 1.10 & 1.9)
Symptoms:
- First monitor through Thunderbolt works fine
- Second (DP1) monitor detected by system settings
- Second monitor shows only black screen
- Can move mouse to black screen - just can't see it