I use a variety of software on a day to day basis, but what I use for videos in particular are:
Video Editing: mostly kdenlive, I do have DaVinci Resolve but I hardly use it (runs really badly on both my PCs)
Thumbnails i use Affinity to make them, but my knowledge of it is very limited
Other Software i use rufus, balena etcher or ventoy for bootable USBs, NTLite for custom windows isos, darktable for editing RAW photos taken with my 550D, and probably more but my mind's blank :(
actually I got some more!!! spotify (with spicetify but it broke), tenacity for recording audio, fl stduio for music, chrome on windows ands firefox on linux etc