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.
for (const std::string& bind_arg : args.GetArgs("-bind")) {
        CService bind_addr;
        const size_t index = bind_arg.rfind('=');
        if (index == std::string::npos) {
            if (Lookup(bind_arg, bind_addr, default_bind_port, *fAllow {
                connOptions.vBinds.push_back(bind_addr);
                if (IsBadPort(bind_addr.GetPort())) {
                    InitWarning(BadPortWarning("-bind", bind_addr.GetPort()));
                }
                continue;
            }
        } else {
            const std::string network_type = bind_arg.substr(index + 1);
            if (network_type == "onion") {
                const std::string truncated_bind_arg = bind_arg.substr(0, index);
                if (Lookup(truncated_bind_arg, bind_addr, BaseParams().OnionServiceTargetPort(), false)) {
                    connOptions.onion_binds.push_back(bind_addr);
                    continue;
                }
            }
        }
        return InitError(ResolveErrMsg("bind", bind_arg));
    }
    for (const std::string& strBind : args.GetArgs("-whitebind")) {
        NetWhitebindPermissions whitebind;
        bilingual_str error;
        if (!NetWhitebindPermissions::TryParse(strBind, whitebind, error)) return InitError(error);
        connOptions.vWhiteBinds.push_back(whitebind);
    }
     If the user did not specify -bind= or -whitebind= then we bind