I think DarkTable is as powerful if not moreso than Lightroom but Lightroom has AI image processing tools that will get things done quicker.

The whole of software dev is dominated with open source softtware. So like PostgreSQL, text editors like Lapce or Zed, KVM/QEMU/Virt-Manager, torrent programs like qBitorrent, VPN like OpenVPN or Wireguard. Pretty much all the video game console emulators. For a while you would get Linux game ports that would use proprietary wrappers but eventually WINE would become better anyways. Don’t know if there’s a proprietary software better than QGIS for that. I love Distrobox and Boxbuddy. Git.

Web browsers based off Chromium or Firefox, OBS, Handbrake, VLC, ffmpeg, image magick. Krita and Blender are competitive with proprietary software. I think the latest Pinta is solid as a paint.net analogue. Audacity is super popular. Ardour for more complex things. Kdenlive isn’t as good but solid enough for the vast majority of people in my opinion.

Topaz Gigapixel is top but Upscayl is good. I always liked Windows Task Manager but on Linux I think Mission Center is just as good. None of the open source stuff competes against Topaz Video AI in my experience

KeepassXC password manager. At some point I stopped using winrar and was all in on 7-Zip and Peazip if not just using the Linux file roller software that the distro came with. I’m happy with Jellyfin over Plex. There’s Kodi. Over the years I always see people use draw.io