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.
}
    LogPrintf("nBestHeight = %d\n", chain_active_height);
    if (node.peerman) node.peerman->SetBestHeight(chain_active_height);
     Map ports with UPnP or NAT-PMP.
    StartMapPort(args.GetBoolArg("-upnp", DEFAULT_UPNP), gArgs.GetBoolArg("-natpmp", DEFAULT_NATPMP));
    CConnman::Options connOptions;
    connOptions.nLocalServices = nLocalServices;
    connOptions.nMaxConnections = nMaxConnections;
    connOptions.m_max_outbound_full_relay = std::min(MAX_OUTBOUND_FULL_RELAY_CONNECTIONS, connOptions.nMaxConnections);
    connOptions.m_max_outbound_block_relay = std::min(MAX_BLOCK_RELAY_ONLY_CONNECTIONS, connOptions.nMaxConnections-connOptions.m_max_outbound_full_relay);
    connOptions.nMaxAddnode = MAX_ADDNODE_CONNECTIONS;
    connOptions.nMaxFeeler = MAX_FEELER_CONNECTIONS;
    connOptions.uiInterface = &uiInterface;
    connOptions.m_banman = node.banman.get();
    connOptions.m_msgproc = node.peerman.get();
    connOptions.nSendBufferMaxSize = 1000 * args.GetIntArg("-maxsendbuffer", DEFAULT_MAXSENDBUFFER);
    connOptions.nReceiveFloodSize = 1000 * args.GetIntArg("-maxreceivebuffer", DEFAULT_MAXRECEIVEBUFFER);
    connOptions.m_added_nodes = args.GetArgs("-addnode");
    connOptions.nMaxOutboundLimit = *opt_max_upload;
    connOptions.m_peer_connect_timeout = peer_connect_timeout;
     Port to bind to if `-bind=addr` is provided without a `:port` suffix.
    const uint16_t default_bind_port =
        static_cast<uint16_t>(args.GetIntArg("-port", Params().GetDefaultPort()));
    const auto BadPortWarning = [](const char* prefix, uint16_t port) {
        return strprintf(_("%s request to listen on port %u. This port is considered \"bad\" and "
                           "thus it is unlikely that any peer will connect to it. See "
                           "docp2p-bad-ports.md for details and a full list."),
                         prefix,
                         port);
    };