The open source microkernel seL4 has been formally verified and is therefore considered to be particularly secure. The Munich start-up Hensoldt Cyber is developing a security chip with the disclosed RISC-V core Ariane from ETH Zurich, which is to run with seL4. It is intended for devices with particularly high security requirements, including weapon systems, critical infrastructures (KRITIS) and vehicles.
article: https://www.heise.de/newsticker/meldung/Bayrischer-RISC-V-Sicherheitschip-mit-seL4-Microkernel-4654021.html