At a previous company we used RT (open source), self hosted: https://bestpractical.com/request-tracker https://bestpractical.com/request-tracker We hooked it

At a previous company we used RT (open source), self hosted: https://bestpractical.com/request-tracker https://bestpractical.com/request-tracker We hooked it into help@company.com emails and also made a web page that allowed customers to ask for support when they were logged in. The web page would add customer details when signed in so the CS staff didn't have to look as much stuff up to answer the question. They have cloud-hosted plans though I have no experience with that.