Add README trivia

README.org

@@ -1,3 +1,4 @@
+
 #+TITLE: Radium on NixOS
 
 Radium (a music creation tool, DAW) derivation for NixOS, fruit of a
@@ -13,7 +14,35 @@ Clone the repository into ~/etc/nixos/~. Next, in
 #+END_SRC
 
 *By default, it builds the demo version of Radium.* How to build the
-full version is left as an exercise to the reader.
+full version is left as an exercise to the reader (it's very simple).
+
+* Common issues
+
+When launching Radium, this is an error you might get:
+
+#+BEGIN_QUOTE
+Plugin Ladspa / Calf MultiChorus LADSPA not found. Replacing with a Pipe.
+#+END_QUOTE
+
+Just ignore this. I don't know why it doesn't find it, Calf plugins
+are bundled in the derivation. Second problem:
+
+#+BEGIN_QUOTE
+Unable to set real time priority. Error code: 1073741824. (EPERM: 1) (errno: 0) (strerror: "Success")
+
+You should:
+
+1. Quit Radium
+2. Stop Jack
+3. Start Jack
+4. Start Radium
+
+On Linux, you might also want to check your system configuration.
+#+END_QUOTE
+
+To fix this, do `jack.jackd.enable = true` to your
+configuration.nix. If you use PipeWire, the JACK emulation doesn't
+work for Radium. You need to use the actual JACK daemon.
 
 * Problems?