Check incoming OSC arguments using Condition

Could you share the string you're trying to send?

One way to do this would be to change your Trigger to ethernet input and configure it for UDP. Since OSC uses UDP for transport. You can structure your input string to contain a <d> or an <s> to capture the value in your message as a variable and then use scripting to check that value.

if trigger == "value" then
    return true
else
    return false
end

I replaced "value" with 1 (the argument received is an integer). Put it in the quick script, and the log said:

17 Sep 10:35:00 Trigger 2000 rejected - conditions were not satisfied
17 Sep 10:35:00 CONDITION Script: script returned false
17 Sep 10:35:00 CONDITION Script: Quick Script executed successfully in 100 microseconds (mem in use = 58KB)
17 Sep 10:35:00 Trigger 2000 (IO Module): Matched
17 Sep 10:35:00 OSC /trigger args: 1

Any idea why it doesn't match?

log what the trigger is to debug

if trigger == 1 then
    return true
else
    log("*** Trigger input is "..trigger.." ***")
    return false
end

I replaced trigger with get_trigger_variable(1) in your original script and it works!