Failed to connect to Nextcloud database: received corrupt message

x86_64$ LOG=DEBUG ./notify_push -- config.php
[2021-05-24 15:26:03.946631 +02:00] DEBUG [rustls::client::hs] /home/runner/.cargo/registry/src/github.com-1ecc6299db9ec823/rustls-0.19.0/src/client/hs.rs:89: No cached session for DNSNameRef("localhost")
[2021-05-24 15:26:03.946674 +02:00] DEBUG [rustls::client::hs] /home/runner/.cargo/registry/src/github.com-1ecc6299db9ec823/rustls-0.19.0/src/client/hs.rs:211: Not resuming any session
Error:
   0: Failed to connect to Nextcloud database
   1: error communicating with the server: received corrupt message
   2: received corrupt message

Location:
   /tmp/krankerl.PNFmShx8gZmS/notify_push/src/storage_mapping.rs:57

Backtrace omitted.
Run with RUST_BACKTRACE=1 environment variable to display it.
Run with RUST_BACKTRACE=full to include source snippets.

Dump-config looks correct:

./notify_push --dump-config config.php
Config {
    database: AnyConnectOptions(
        MySql(
            MySqlConnectOptions {
                host: "localhost",
                port: 3306,
                socket: Some(
                    "/var/run/mysqld/mysqld.sock",
                ),
                username: "nextcloud",
                password: Some(
                    "XXXXXXXXXX",
                ),
                database: Some(
                    "nextcloud",
                ),
                ssl_mode: Preferred,
                ssl_ca: None,
                statement_cache_capacity: 100,
                charset: "utf8mb4",
                collation: None,
                log_settings: LogSettings {
                    statements_level: Info,
                    slow_statements_level: Warn,
                    slow_statements_duration: 1s,
                },
            },
        ),
    ),
    database_prefix: "oc_",
    redis: [
        ConnectionInfo {
            addr: Unix(
                "/var/run/redis/redis.sock",
            ),
            db: 0,
            username: None,
            passwd: None,
        },
    ],
    nextcloud_url: "https://XXX.XXX.XX/",
    metrics_bind: None,
    log_level: "DEBUG",
    bind: Tcp(
        0.0.0.0:7867,
    ),
    allow_self_signed: false,
}

It seems to be as if the tools tries to establish an TLS connecion over the local unix socket what does not make any sense.

Using 127.0.0.1 as DB host also doesn't work (failing with InvalidDNSNameError what is correct, using the hostname in the server certificate doesn't work too with the very same error "received corrupt message"),

How can the ssl_mode config be controlled?

System:

• Debian 10.9
• DB: MariaDB 10.3
• PHP 8.0
• ./notify_push --version: notify_push 0.1.7

Start at src/storage_mapping.rs:57 and reproduce the failure with the shown notify_push command and config.php on MariaDB 10.3. Inspect how the database connection and ssl_mode are selected, then verify the behavior with the reported Unix-socket and host configurations. Done means the connection handles the configured transport without the corrupt-message error or clearly reports an unsupported configuration.