2020-12-15 20:38:03 0 [ERROR] InnoDB: Invalid log block checksum. block: 811904837 checkpoint no: 10978 expected: 3929835436 found: 881240600

This causes user confusion because it is a transient error that can be retried and overcome. Per Marko: {
--backup will invoke the function in a loop:

for (int retries= 0; retries < 100; retries++) {

    if (log_sys.log.read_log_seg(&lsn, end_lsn)

    || lsn != start_lsn) {

        break;

    }

    msg("Retrying read of log at LSN=" LSN_PF, lsn);

    my_sleep(1000);

}

If the function log_t::files::read_log_seg() fails, it will display the message:

ib::error() << "Invalid log block checksum."

<< " block: " << block_number

<< " checkpoint no: "

<< log_block_get_checkpoint_no(buf)

<< " expected: " << crc

<< " found: " << cksum;

If you are also seeing the "Retrying read of log" message, there should be nothing to worry about. Due to the inter-process communication via the file system, Mariabackup must be prepared to retry reading data pages (innodb_page_size bytes) or log blocks (512 bytes) that appear corrupted.
}

So could this be changed to a [Warning] until it stops retrying?