I really like Syncthing, Nextcloud, Forgejo and Mailcow to collaborate with colleagues.
Kimai allows me to track hours and get paid.
Barrier allows me to use several computers at once.
Xen Orchestra is pretty much on par with VMWare stuff and way cheaper.
What other awesome software does allow you to work more efficiently in a business context and stays out of your way?
My worker cooperative helps authors self-publish, and we use as much open-source as possible to do that. We rely almost exclusively on a number of tools which are all better than proprietary counterparts for one reason or another (sometimes merely because they are free and allow us to keep costs minimal) but the main reason is most of our clients value unquestioned data ownership over anything else. We avoid corporate cloud services and self-host as much as possible, for example.
Having said that, IMO many of these are also better designed and better UI than comparable paid tools. Blender being the obvious best example, but WordPress is another one. I used to ignorantly shit on WP so much when I was working in the professional startup industry as a web developer. Since then, I’ve learned to my delight that it’s awesome if you don’t bog it down with a bunch of horrible plugins, and the latest versions with their block editor approach are so good for easy and quick theming.
Here’s a list off the top of my head of our regularly used software. I’m sure I’m forgetting some, and many of these are going to be unsurprising: