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You could connect to an on-premise server. As a bonus, the manufacturer cannot disable them and extort money in this case.
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They most likely are. Third party techs then access them over Citrix or VPN/RDP. There could be some cloud portion that aggregates data or pushes policies and schedules as well.
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If the only usecase is monitoring, then why make the fridges anything else but report-only?

No firmware updates. no admin configuration. no ssh backdoors. just a transmit-only system

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because the report code might have bugs
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If it were transmit only, you could put it behind a data diode and buggy report code wouldn't matter. Even better, validating the code is a lot easier if it doesn't accept attacker input.
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Monitoring requires one-way announcements, not bi-directional connections
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