This is a windows program written in delphi. A fitting choice, because Delphi provides both the necessary data grid component and the syntax highlighting editor, as well as connectors to several sql databases.

A cross platform version could be written in Lazarus, with the idea that it uses less system resources than a large java program.

I was forced to switch to DBeaver as HeidiSQL isn't allowed at my current employer. I miss how light Heidi is, but I'm not sure I'd switch back now I'm used to all the features DBeaver has.

I use a mac and linux now. I think HeidiSQL is the thing I miss most from Windows.

Someone started a cross-platform rewrite at https://github.com/ragnar-lodbrok/meow-sql which has made incredible progress.

Have they fixed the awful stability issues and the fact that a query that takes longer than ~5s will lock up the entire application until it completes?

I also use HeidiSQL almost daily. Besides MySQL / MariaDB it also can connect to MSSQL and Postgres.

I recently had to import a CSV with some million rows into MariaDB. Neither HeidiSQL nor DBeaver could do it (tried various settings). IntelliJ worked like a charm.