diff --git a/static/usage.html b/static/usage.html
index d0264e36..c954d5a9 100644
--- a/static/usage.html
+++ b/static/usage.html
@@ -1128,6 +1128,13 @@
                 It is not possible to change the IMEI on a production device and GrapheneOS will never add
                 support for this.</p>
                 
+                <p>Android 12 introduced support for the <a href="https://www.gsma.com/newsroom/wp-content/uploads//TS.43-v8.0-2.pdf">GSMA TS.43</a> standard, where provisioning for VoLTE,
+                VoNR, Wi-Fi calling may be handled by Google Firebase. Currently it is very rare for 
+                carriers to be using Firebase to handle this. It is unlikely, but technically possible, that 
+                with such carriers, you may be required to install sandboxed Google Play in order to obtain the
+                former mentioned functionality where the carrier has not implemented fallback provisioning via SMS. 
+                Currently only US Cellular, Orange France, Cspire US, Cellcom US are using this standard.</p>
+
                 <p>GrapheneOS includes bypasses for carrier restrictions on APN editing, tethering via
                 USB, Ethernet, Bluetooth and Wi-Fi and the ability to disable 2G, actions which would not
                 necessarily have been possible on the stock operating system.</p>