Install instructions: https://github.com/DigasNikas/pomium/blob/main/docs/install.md
macOS — download the .dmg, open it, drag Pomium to Applications.
Windows — download the .exe and run it.
npm — npm install -g pomium (skips both warnings above, pulls Electron through npm instead).
Both installers are unsigned, so the first launch shows a warning. The install guide above walks through it.