xr500 RIP? Where is the SPI and NAT? Borrowed Linksys Gui? No SSH/Telnet?

So I purchased this XR500 based on the understanding that there was NAT support and SPI built into the firewall but I can't seem to find any configuration option other than old school vulnerability based RIP protocol?

What configuration options were you expecting for NAT & SPI? It mentions them as features but that doesn't automatically mean you're able to configure everything to do with it. NAT Filtering is available in WAN Setup.

I am a bit surprised at how different the feature set is from what's offered on your R1 router and also the striking resembalance in the GUI as well as feature sets, page layout etc., is to the stock linksys firmware.

I'm not sure what you mean considering there is vastly more offered on DumaOS currently than the R1. VPN Hybrid will be included in one of the next upgrades. Were you an R1 user?

DumaOS is a completely new operating system, technologically far more advanced than any other router software. The UI is unlike any other e.g. pinnable panels. We're very proud of our UI and it has a lot of unique features.

I am a bit taken a back at by how crude this router feature set is for how it's marketed, the fact core marketed features are missing or simply not there

What features are missing? All features that have been marketed are available and there is lots more on the way.

Also, I can't SSH or Telnet into the router?

Telnet is possible but there is no reason a normal user would need this. What are you trying to achieve with Telnet?