proxmox-disable-subscription-popup.patch

--- /usr/share/javascript/proxmox-widget-toolkit/proxmoxlib.js	2020-06-30 13:36:05.000000000 +0200
+++ /usr/share/javascript/proxmox-widget-toolkit/proxmoxlib.js-new	2020-07-12 12:43:34.704855306 +0200
@@ -450,6 +450,9 @@
     },
 
     checked_command: function(orig_cmd) {
+	orig_cmd();
+	return; // Neutralize the API request
+
 	Proxmox.Utils.API2Request(
 	    {
		url: '/nodes/localhost/subscription',

You can apply it with this one-liner:

curl https://gist.githubusercontent.com/Zoddo/828c66e46b0d6ae0d70da24e4149e391/raw/cb18ba255f35b7582e9ce4f122dcc175764419d5/proxmox-disable-subscription-popup.patch | patch -p0 -d /

If you want, you can apply it automatically on reboot or on whatever event happens by executing this bash command (it detect if the patch is already applied):

patch -p0 -d / -N -r - < proxmox-disable-subscription-popup.patch

#!/bin/bash

read -r -d '' PATCH << EOF
--- /usr/share/javascript/proxmox-widget-toolkit/proxmoxlib.js	2020-06-30 13:36:05.000000000 +0200
+++ /usr/share/javascript/proxmox-widget-toolkit/proxmoxlib.js-new	2020-07-12 12:43:34.704855306 +0200
@@ -450,6 +450,9 @@
     },
 
     checked_command: function(orig_cmd) {
+	orig_cmd();
+	return; // Neutralize the API request
+
 	Proxmox.Utils.API2Request(
 	    {
		url: '/nodes/localhost/subscription',
EOF

echo "$PATCH" | patch -p0 -d / -N -r -

service pveproxy restart
echo 'Patch successfully applied!'

Edited by @Zoddo on 16/04/2021 to includes changes for last versions

Updated patch file for last versions