A bit more niche, is Weasis - Dicom Browser for medical images. Alternative is also ImageJ which is used a lot in for scans too.

I still can’t get used to calling programs apps

The Dialer.

• Comes with every phone
• 10+ digit number instantly connects you with millions of people, services, and institutions
• 3 digits connects you with life-saving emergency support
• Very low-latency voice support
• High quality audio (most of the time)
• No ads
• No obnoxious UI

All kidding aside, I’m routinely astounded at how we have yet to top the ease and utility of old-fashioned phone service.

Librewolf, FFmpeg, Vim, Wine

OBS, and Blender. Two industry shaping software solutions that ere fully open source and free.

uBlock Origin leading the pack by at least a furlong.

KiCad. GNU Linux. Blender. Gqrx. Rclone. Syncthing

Home Assistant, not only an App but it changed the way i look at IoT/Smarthome and in that way it brings me a lot of comfort.

7 zip, VLC, Paint.net, proxmox, home assistant

Linux

LocalSend, Immich, Signal, Aurora store, Radio Garden, Gray Jay, yt-dlp, and Bitwarden just to name a few

YouTube clients like NewPipe

Signal. Highly secure communication. No ads. Easy to use.

Proton. Literally makes any of the big linuxes into the streamos people are waiting for

Libre Office