Unclear RF Schematic Reference for Power Amplifier Connection and Matching Network Properties
Quick partial answer with docs that have become available since your wrote your question:
ST has published a pretty good app note AN5457 on the matching network design: https://www.st.com/resource/en/application_note/dm00690797-rf-matching-network-design-guide-for-stm32wl-series-stmicroelectronics.pdf
You can also find specific component values in the BOM for the Nucleo WL55JC docs: https://www.st.com/content/st_com/en/products/evaluation-tools/product-evaluation-tools/mcu-mpu-eval-tools/stm32-mcu-mpu-eval-tools/stm32-nucleo-boards/nucleo-wl55jc.html and there's a schematic for a not-yet-published reference board on the ST forum:  https://community.st.com/s/question/0D53W00000FzAd6SAF/mb1552b-board-stm32wl-reference-layout-bom-and-schematic-
Finally, there are sx1262 docs and reference layouts on Semtech's site.
I still found it a mess to track down all the details 'cause the docs are scattered, but it's not a wild guessing game anymore.