I work on B2B SaaS applications for medium/large industrial company and I don't think open source would improve your security posture for this type of client. IT departments have to evaluate vendors against a set of criteria and you pass or fail. if they are worried about the confidentiality of their data, then another approach would be to let them run your chatbot in their own cloud environment (or on premises).
this approach is appealing for a lot of companies. for instance, just looking at Azure, if you make your application part of the MS Transact program, then the client would simply pay their monthly/annual azure subscription and your license would just be a line item on it. this may seem pointless but large corp tend to negotiate deals with cloud providers and negotiate a better deal provide they spend a certain amount per year. if your solution helps them achieve this amount, it's very appealing
Beyond that, you can work on complying with SOCII or other programs