Hi @Hermanfr ,

I worked with JMETER in the past. This load and functional test suite is available on premise. You simply have to make sure that you install it in your datacenter somehow.  The Apache JMeter application is open source software, a 100% pure Java application designed to load test functional behavior and measure performance. It was originally designed for testing Web Applications but has since expanded to other test functions.

https://support.servicenow.com/kb?id=kb_article_view&sysparm_article=KB0687724

I never used it together with ServiceNow but is is worth to try (hopefully).