docs(client/linux): document known issue with ZFS (#6756)

`atomicwrites` will have a fix soon probably
https://github.com/untitaker/rust-atomicwrites/pull/64, but if they
don't, we should document it

website/src/app/kb/client-apps/linux-client/readme.mdx

@@ -267,6 +267,7 @@ sudo mv /etc/resolv.conf.before-firezone /etc/resolv.conf
 
 ## Known issues
 
-None at time of writing.
+- The Linux Headless Client may throw an error on ZFS when generating its device
+  ID [#6704](https://github.com/firezone/firezone/issues/6704)
 
 <SupportOptions />

website/src/app/kb/client-apps/linux-gui-client/readme.mdx

@@ -213,5 +213,7 @@ the tunnel, and a GUI which allows the user to control Firezone.
   [#4883](https://github.com/firezone/firezone/issues/4883)
 - If you update Firezone while the GUI is running, you must manually restart the
   GUI [#5790](https://github.com/firezone/firezone/issues/5952)
+- The Linux GUI Client does not work on ZFS yet
+  [#6704](https://github.com/firezone/firezone/issues/6704)
 
 <SupportOptions />