The recent kernel patch that fixes the rcu errors/crashes has been applied to U-Boot in Manjaro testing/unstable branches. https://gitlab.manjaro.org/manjaro-arm/packages/core/uboot-pinephone/-/commit/ebdfd9a4124276fdb2d636aaecb861c205b71d69 I have tested this on the 4 phones that randomly hang during boot. All 4 have passed 100 consecutive reboot cycles without hanging. Hopefully this patch makes it into other distributions soon.
Some random posts about the pine64 pinephone