Thanks for the extra context. I would suggest avoiding traditional dicom networking (DIMSE) in a cloud environment. TLS would only give you encryption of the network traffic, not real protection from hackers or other security issues. A VPN would be better, or you can tunnel with ssh. But still, my understanding is that DIMSE is not efficient over wide area networks.
You should look at DICOMweb as an alternative because you can use state of the art web security methods. For example Slicer’s DICOMweb extension can use a Google dicom store that authenticates with a Google account so you have finer grained access control. I haven’t used it, but I understand Orthanc supports DICOMweb, as does dcm4chee.
In terms of web viewers you may wish to look at OHIF.
You are correct that Slicer is not intended for clinical use as-is so be sure to follow local laws and institutional practices. But yes, MONAI is very promising for ML work and many clinicians use Slicer for their research studies.