So I run Pat for winlink capability...

I don't support PAT. I do support paclink-unix and mutt, claws-mail, rainloop
mail apps

...I started having a lot of timeout problems so I was monitoring axlisten...

Where did you get axlisten? The NWDR image comes with listen.

There I noticed a problem with Chromium. ...Chromium is apparently
broadcasting Upnp info over the udr0: port...triggering the radio to
transmit...and or interrupting other packet comm and completely
screwing up the data transmission.

The NWDR image comes configured with iptables to prevent that. I take it
you are not using the NWDR image? iptables gets setup when you run
./app_config.sh core if you follow the "Getting Started Guide".
https://nw-digital-radio.groups.io/g/udrc/wiki/8921

Is there something in the Draws config that can stop that...or are the
IP address ports for udr0 and udr1 enabling it

Yes I am well aware of the Chromecast problem, as well as
Bonjour/Multicast DNS, Dropbox, Samba broadcasts. All of those apps bind
to all Network interfaces. iptables fixes that.

I know that Pat is not part of Draws...but Chromium comes
installed...and whenever Chromium is running it attempts to send
packets over udr0:

Anywhere I can look for info?

udr0: fm KF5xxx-10 to QST ctl UI pid=CC(IP) len 195 13:13:34IP: len 195
192.168.255.2->239.255.255.250 ihl 20 ttl 1 DF prot UDPUDP: len 175
58661->1900 Data 167M-SEARCH * HTTP/1.1HOST: 239.255.255.250:1900MAN:
"ssdp:discover"MX: 1ST: urn:dial-multiscreen-org:service:dial:1USER-AGENT:
Chromium/78.0.3904.108 Linux