Did you just use standard Yocto or similar tools to build such images? Are there standard daemons for managing hardware watchdogs (besides systemd since that's too simple as you say)? I think there's a lot of niche knowledge in the embedded space and many programmers are used to cloud systems and at most target. The most embedded experience most programmers have is likely iOS/Android development where all of the actual embedded concerns are handled for you. Even Google (soft)bricked a bunch of phones with the latest Android 14 update [1].

IMO there's not a lot of regular OSS for building embedded systems that comes with A/B partitioning, watchdogs, secure and verified boot - it's all custom at every org and tailored for individual products.

[1] https://arstechnica.com/gadgets/2023/11/android-14-patches-r...