Now about some more 'niche' things I tend to and software I use for it: Speedrunning and acting as a moderator/verifier for several games on https://speedrun.com.
To retime runs to the frame I use Shotcut. To download the runs from people's YouTube channels I use YouTube Downloader. Both are available for Linux & work perfectly well.
I also tried out speedrunning on Ubuntu. I managed to install OBS and recorded several sessions without issue. Then I used OpenShot to cut the footage. I also tried out Krita to create a thumbnail. Everything worked fine, it didn't take too long to get used to the last two even though I'm used to Movavi and Photoshop. I didn't actually use the thumbnail I made in Krita because it looks so much less refined than my Photoshop thumbnails! But it works. And everything's free.
Recorded and cut on Linux: https://youtu.be/0MPeQ-WPOfU?si=-CBDZoC8aKBJ7o8g
Enjoy the makeshift thumbnail I didn't end up uploading. (Now that I'm looking at it again it's not even that bad.)