Off the top of my head from daily use;
- Borg backup, powerful backup software for self-hosted oriented users or enterprise automation.
- proxmox, hypervisor that is performant and easy to setup for simple and complex virtualization needs.
- bitwarden (combined with vaultwarden self-host), password management, secrets management, and available on basically all platforms and browsers. Self hosting your vault gives you peace of mind over who has your most sensitive data.
- obsidian, a great notes app with polished cross platform applications that don’t do any funky proprietary storage shenanigans. Files are files and folders are folders.
- kate (and most of the KDE suite), premiere Linux desktop environment suitable for customization and all the expected luxuries user would expect from windows or macOS. Kate specifically is a noticeable modern upgrade over notepad++ and rivals VSCode for programmers.