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?
Wordpress even has activitypub integration now! Hooray! Here's hoping automattic do good on their word and bring it to their other projects like Tumblr
Also as much as I like gimp, it is unfortunately not that widely used due to super specialised and hard to use compared to the industry standard juggernaut that is adobe's creative suite. You're probably going to get laughed at in any professional industry if you suggest seriously using it.