If you’re on linux:

For video editing, one of the simpler but still feature-full ones is Openshot. If all you need is trimming, then Lossless Cut or the mpv plugin ‘mpv-lossless-cut’ is good.

edit: not sure if openshot is open source tbh

As for images, I don’t have any experience so maybe just check the ones here in section 2.5: https://wiki.archlinux.org/title/List_of_applications/Multimedia