One of the things the iPhone can do (if enabled in settings) is it can automatically switch data to the 2nd sim/esim if the primary sim/esim has no service (out of coverage).

I've not seen this implemented in android phones, assuming apple doesn't have a patent on it is it something Graphine OS could do?

It's not perfect as for it to switch over the primary sim has to have no connection at all (So if there's even 2G/GPRS it will stick to the primary) but it does occasionally come in handy when in more rural locations with spotty coverage.