The expanding massive smart internet of things (IoTs) sensors with emerging use cases have created legitimate security requirements concerns for device manufacturers. Within decentralised and distributed systems of smart IoTs devices, heterogeneous mix of wireless protocols and/or standards are deployed. These technologies enable short-range (proximity and wireless personal area network); short/medium-range (wireless local area network); medium-range (wireless neighbourhood area network); and long-range (wireless wide area network) connectivities. The 5G/6G convergence ecosystem will span edge, gateway and enterprise IoTs nodes with unique security requirements. The public key infrastructure (PKI) is currently the industry’s holy grail for building secure IoTs devices. However, the current design solutions lack post-manufacturing multi-radio dynamic key reconfiguration and integrated reconfigurable hardware solutions. PKI must be embedded into the hardware design and simplified for third-party developers and manufacturers to implement and deploy. In this paper, we propose dynamic key configuration protocol (DKCP) and reconfigurable hardware root of trust (RHRoT) for 5G/6G satellite-cellular convergence network IoTs PKI implementations. This hybrid hardware-application protocol security solution provides a three-tier authentication that can be optionally implemented depending on the threat level within the IoTs device environment. Hence, DKCP only; DKCP and RHRoT; and RHRoT only tiers can be implemented to achieve IoTs PKI-based authentication, encryption and integrity for devices at scale by device manufacturers with little or no cryptography knowledge. The proposed adaptive IoTs PKI model promises scalable ubiquitous, seamless, cost-effective, secure, simple and security solution to stay ahead of existing and emerging threats and regulations.