Mobile connectivity (4G) support for HA yellow

[lilac belfry]

I'm looking to setup HA and I'm currently oriented towards Home Assistant Yellow. As I would like to also use HA for a security alarm system I'm looking for options to add as a backup mobile connectivity via a cellular 4G network with a SIM card.
Is there any compatible HAT or similar hardware solution that I could use to add mobile connectivity to HA Yellow?
If not, what kind of hardware setup would you suggest to achieve the same capabilities of HA Yellow + mobile connectivity?

[rancid radish]

I think you will probably want to have a separate device to run your cellular connection. you could add a 2nd network interface by USB though I believe to connect to it.
you will also need to have some kind of tunnel setup to use it as a cellular connection wont (usually) be able to accept direct incoming connections.

does this have to be dedicated to your HA setup? a better solution is maybe to look network wide and have a router that supports having a 4g fallback for the network. you still need to have things set up as a tunnel but they should automatigically switch over with the network fallback

[lilac belfry]

Thanks for your ideas. I thought about doing that more globally but from one side I don't have much else that could benefit from a cellular backup and the router I have is provided by my current ISP and doesn't have support for cellular backup unfortunately.
Hence why I'm looking more for a solution related to HA and need to decide if is better to have HA Yellow + something else or install HA on a different hardware setup that allows to have cellular backup.

[rancid radish]

a dedicated 4g router and an additional network interface for the yellow (by usb) is probably the route i would go. just ensure that the lan side of the 4g router doesnt clash with your main ip address range otherwise all hell is gunna break loose