On my Linux Mint 19.1:
```bash
$ umask
0022
```

After the first run of `bitcoin-qt -sysperm=false` the `0700` permissions are expected for both the datadir (`~/.bitcoin`) and the walletdir (`~/.bitcoin/wallets`).

Actually, the directories are created with such access permissions:
```bash
$ stat ~/.bitcoin | grep Uid
Access: (0755/drwxr-xr-x)  Uid: ( 1000/ hebasto)   Gid: ( 1000/ hebasto)
$ stat ~/.bitcoin/wallets | grep Uid
Access: (0755/drwxr-xr-x)  Uid: ( 1000/ hebasto)   Gid: ( 1000/ hebasto)
```

Refs:
- #4286
- #13371
- #13389

NOTE: reading through the initial PR #4286 makes me think it was controversial. Is it a better and simpler way to just get rid of `-sysperm` option? I believe a user who needs this option can easily run `chown` command.
{
    ArgsManager& args = *Assert(node.args);
    if (args.GetBoolArg("-disablewallet", DEFAULT_DISABLE_WALLET)) {
        LogPrintf("Wallet disabled!\n");
        return;
    }
    auto wallet_loader = node.init->makeWalletLoader(*node.chain);
    node.wallet_loader = wallet_loader.get();
    node.chain_clients.emplace_back(std::move(wallet_loader));
}
} 
const WalletInitInterface& g_wallet_init_interface = wallet::WalletInit();