I just faced a problem in STMCube MX for STM32L053R8T6, there is no option to select alternative function OPEN DRAIN output for LPUART1.
I see the option for USART1 or USART2 GPIO settings but not for LPUART1.
I First thought that option is not available for LPUART peripheral, so checked all datasheet's related pages ... but didn't find any note about it.
Finally i changed the generated code (LPUART1 MspInit part) manually and set the TX pin of LPUART1 output mode to GPIO_MODE_AF_OD, then it worked.
I just wanted to inform you to correct this bug in the software for future.
The Installed package for L0 series in STMCube is V1.10.0 (The last update).
Thanks & Regards.