How to lock android tablet for web browsing only?
The simplest approach is probably to use Google's Android Management API, it's compatible with all Android devices running Android 5.1 or above.

To lock the device on one app, or on multiple app, you define a kiosk policy like below:



"applications": [
 {
   "packageName": "com.example.app",
   "installType": "FORCE_INSTALLED",
   "lockTaskAllowed": true,
   "defaultPermissionPolicy": "GRANT",
 },
 {
   "packageName": "com.example.app2",
   "installType": "FORCE_INSTALLED",
   "lockTaskAllowed": true,
   "defaultPermissionPolicy": "GRANT",
 }
"persistentPreferredActivities": [
  {
    "receiverActivity": "com.example.app/.com.example.app.MainActivity",
    "actions": [
      "android.intent.action.MAIN"
    ],
    "categories": [
      "android.intent.category.HOME",
      "android.intent.category.DEFAULT"
    ]
  }
]