Based on previous answers, including from Ikhtesam, I managed the following:

$workflowUri = "/subscriptions/$SubscriptionId/resourceGroups/$ResourceGroup/providers/Microsoft.Web/sites/$LogicAppName/workflows/"
$workflows = az resource show --ids $workflowUri | ConvertFrom-Json
foreach ($workflow in $workflows.value) {
    $workflowName = $workflow.name -replace "$LogicAppName/", ""
    $triggerUri = "https://management.azure.com/subscriptions/$SubscriptionId/resourceGroups/$ResourceGroup/providers/Microsoft.Web/sites/$LogicAppName/hostruntime/runtime/webhooks/workflow/api/management/workflows/$workflowName/triggers/$TriggerName/listCallbackUrl?api-version=2018-11-01"
    $response = az rest --method post --uri $triggerUri | ConvertFrom-Json
    Write-Output $response.value
}