How to make sure Electrum connects to my private Electrs server and to no other server?

[Bitcoin]

How to make sure Electrum connects to my private Electrs server and to no other server?

I want to connect my Electrum wallet app to my private Electrs server in my local LAN which is also reachable via onion. I want to just use this one server, no other server. My ~/.electrum/config is

{
    "alias": "",
    "auto_connect": false,
    "blockchain_preferred_block": {
        "hash": "000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f",
        "height": 0
    },
    "check_updates": true,
    "config_version": 3,
    "gui_last_wallet": "/Users/$USER/.electrum/wallets/default_wallet",
    "is_maximized": false,
    "oneserver": false,
    "proxy": "socks5:127.0.0.1:9050::",
    "recently_open": [
        "/Users/$USER/.electrum/wallets/default_wallet"
    ],
    "rpcpassword": "",
    "rpcuser": "",
    "server": "something.onion:50002:s",
    "show_channels_tab": true
}

This seems to work fine in the sense that I am connected. But I have a lot of nodes in my list under the "Network" settings in Electrum. And this is because the oneserver property is set to false. If I try to set it to true in the config manually, Electrum starts and works fine but the config file is reverted to its old state with false in it.

How can I make sure this works?

Source: How to make sure Electrum connects to my private Electrs server and to no other server?