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.
{
#ifdef USE_BDB
     if (!BerkeleyDatabaseSanityCheck()) {
         return InitError(Untranslated("A version conflict was detected between the run-time BerkeleyDB library and the one used during compilation."));
     }
#endif
    if (gArgs.GetBoolArg("-disablewallet", DEFAULT_DISABLE_WALLET)) {
        for (const std::string& wallet : gArgs.GetArgs("-wallet")) {
            LogPrintf("%s: parameter interaction: -disablewallet -> ignoring -wallet=%s\n", __func__, wallet);
        }
        return true;
    }
    if (gArgs.GetBoolArg("-blocksonly", DEFAULT_BLOCKSONLY) && gArgs.SoftSetBoolArg("-walletbroadcast", false)) {
        LogPrintf("%s: parameter interaction: -blocksonly=1 -> setting -walletbroadcast=0\n", __func__);
    }
    if (gArgs.IsArgSet("-zapwallettxes")) {
        return InitError(Untranslated("-zapwallettxes has been removed. If you are attempting to remove a stuck transaction from your wallet, please use abandontransaction instead."));
    }
    if (gArgs.GetBoolArg("-sysperms", false))
        return InitError(Untranslated("-sysperms is not allowed in combination with enabled wallet functionality"));
    return true;
}
void WalletInit::Construct(NodeContext& node) const