Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/Silicon Labs/Series1/EFR32BG1B/EFR32BG1B232F256GM48/CMU/LFBPRESC0#0x0
LEUART0=DIV1
Low Frequency B Prescaler Register 0 (Async Reg)
Low Energy UART 0 Prescaler
0 (DIV1): LFBCLKLEUART0 = LFBCLK
1 (DIV2): LFBCLKLEUART0 = LFBCLK/2
2 (DIV4): LFBCLKLEUART0 = LFBCLK/4
3 (DIV8): LFBCLKLEUART0 = LFBCLK/8
https://github.com/cmsis-svd/cmsis-svd-data