I'm facing the same issue: using OMV 5.x on Proxmox on a new x86 system
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= OS/Debian information
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No LSB modules are available.
Distributor ID: Debian
Description: Debian GNU/Linux 10 (buster)
Release: 10
Codename: buster
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= openmediavault information
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Release: 5.5.3-1
Codename: Usul