You can directly check with ST about their LoRaWAN dev board with Relay. I have no experience with it and if you back read, @BennuEng has a working relay port for RAK3172. Maybe you can reach out to him to get some hints.
ST released v1.5.0 of their STM32WLxx firmware package with support for LBM and LBM+Relay in February. Initial test on a Seeed Wio-E5 was painless.
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