For software development, we've used C# Windows Form, and obviously more recently, we've used WPF for Window software. We've not done any cross platform software GUI development, as have had no requirements for it. Most cross platform we've written is a command line application for our internal server work, originally C# Mono, but this has been replaced with C++ with the odd little utility being done in Python.
We have done a fair amount of web development work from our website, our support portal and our status pages as well as some projects that are no longer available for a variety of different reasons.
For mobile development we've mostly done Android development using Java. We have done a small amount in Kotlin, but don't have any plans to move away from Java unless we have to (to be honest, we were not a fan of Kotlin, for the main reason being readability felt a lot harder than in Java and other languages we've developed in.
We've developed Boardies MySQL Manager which is our most recent project, and we have plans for other projects and we also plan for this to have a from the ground up rewrite.
We have plenty of expertise in cloud management from managing virtual servers, load balancers and cloud firewalls. Our servers are currently using Digital Ocean and the website is protected using Cloudflare. We plan on expanding our knowledge in cloud management more and more as time goes on based on projects we have on our road map so watch this space.