hello and welcome to the forum,
to generate the md5 in python
password = b'12345678901234567890123456789012'
encryption_key_md5 = base64.b64encode(hashlib.md5(password).digest())
print(encryption_key_md5)
b'dnF5x6K/8ZZRzpfSlMMM+w=='
and the remote would look like
[wasabi_ssectest_remote]
type = s3
provider = Wasabi
access_key_id = redacted
secret_access_key = redacted
endpoint = s3.us-east-2.wasabisys.com
sse_customer_algorithm = AES256
sse_customer_key = 12345678901234567890123456789012
sse_customer_key_md5 = dnF5x6K/8ZZRzpfSlMMM+w==