Which discovery method are you using? Default or mDNS? See lxi-gui preferences
Default, see terminal copy/paste below:
pi@raspberrypi:~ $ lxi discover -m
Searching for LXI devices - please wait...
No services found
pi@raspberrypi:~ $ lxi discover
Searching for LXI devices - please wait...
Broadcasting on interface lo
Broadcasting on interface eth0
Found "Siglent Technologies,SDS2504X Plus,SDS2PDDxxxxxxx,5.0.1.3.9R6" on address 192.168.178.83
Found "Siglent Technologies,SVA1032X,XXXXXXXXXX,3.2.2.5.0.r8" on address 192.168.178.80
Found "Rigol Technologies,DG1062Z,DG1ZAxxxxxxxx,03.01.12 " on address 192.168.178.102
Found "RIGOL TECHNOLOGIES,DP832A,DP8Cxxxxxxxxx,01.01.16" on address 192.168.178.101
Found "RIGOL TECHNOLOGIES,DS1104Z,DS1ZAxxxxxxxxx,00.04.05.SP2" on address 192.168.178.100
Found 5 devices
pi@raspberrypi:~ $ lxi scpi -a 192.168.178.103 *IDN?
Rigol Technologies,DM3068,DM3O222400340,01.01.00.01.10.00
pi@raspberrypi:~ $
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P.S. I can't run lxi-gui atm due to the error described above. Serials replaced by xxxx's