Mesa 7i96 driver/setup Plasma Table

Note: Using POSIX non-realtime
hm2_eth: rtapi_app)main: Connection refused (-111)

The first error is because you are not using a Preempt-RT kernel

You can check with uname -a, the response should include "PREEMPT RT"
Did you follow the instructions here:

linuxcnc.org/docs/html/getting-started/g...th_preempt_rt_kernel

Not sure what the second error is all about, Ive never seen it before

A perhaps simpler path is to try the LinuxCNC Stretch test ISO image

www.linuxcnc.org/testing-stretch-rtpreempt/

and then install a uspace version of LinuxCNC master for Stretch:

deb buildbot.linuxcnc.org/ stretch master-rtpreempt

I've: installed Stretch, manually updated the repositories, installed uspace and successfully pinged the mesa card and manually configured network... kind of...

Getting the same error:
Note: Using POSIX realtime <--- wtf?
hm2_eth: rtapi_app_main: Connection refused (-111)

Currently operating under 4.9.0-5rt-amd64 #1 SMP PREEEMPT RT Debian 4.9.65-3

As far as I can tell, Preempt-RT is completely enabled (error still says "Note: POSIX real time", no clue why); I did however discover that Stretch departs from eth(0/1) and instead uses, in my case, enp5s0 (enp6s0, enp8s0, enp0s31f6).

Could this be affecting the hm2_eth module in linuxcnc? I may be showing my ignorance here, I just can't for the life of me figure out why this is still an issue.

You had this before (which means no real time Preempt-RT kernel:
Note: Using POSIX non-realtime
Now you have this:
Note: Using POSIX realtime
This is correct

I suspect the "Connection refused" issue is something wrong with your network setup

what is the result of running the command:
ip a

on your machine?

Damn... how is this possible; what else do I need to do?

~$ ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: enp5s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 1c:6f:65:cd:65:12 brd ff:ff:ff:ff:ff:ff
inet 192.168.0.30/24 brd 192.168.0.255 scope global dynamic enp5s0
valid_lft 66722sec preferred_lft 66722sec
inet6 fe80::b59e:571b:1798:c3ad/64 scope link
valid_lft forever preferred_lft forever

OK so it looks like your only Ethernet hardware is setup for the wrong address

Did you read the hm2_eth manual page about setting up a static IP address on the host?

Suggested host address is 10.10.10.1 if the 7I92 is setup for 10.10.10.10