Mostly Microsoft SQL Server - both on client's own servers and cloud hosted in Azure.
We use Entity Framework core as the object-relational mapper
We use Joomla to build CMS (Content Management System) based web sites.
For bespoke work we use Microsoft Blazor, often hosted on an Azure App Service. We develop on Visual Studio in C# and use our own Gitlab server (hosted on an Azure virtual Linux machine for source control. HBC have a developer's licence for Telerik Controls that supplement the Blazor environment, Mudblazor is our chosen CSS framework for responsive design.
HBC started using Microsoft Access in 1996 and and have written hundreds of Access apps since then, many of which are still in regular use after 20 years! A front end written in Access, combined with a SQL database, can provide a robust and economical solution to many business problems.