Yes, you can use a USB serial device e.g. /dev/ttyUSB0 see emontx direct serial example for emonhub:

[interfacers]
### This interfacer manages the EmonTx3 ESP format serial
[[SerialTx3e]]
     Type = EmonHubTx3eInterfacer
      [[[init_settings]]]
           com_port= /dev/ttyUSB0
           com_baud = 115200
      [[[runtimesettings]]]
           pubchannels = ToEmonCMS,
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