Many have already mentioned Obsidian, I too ventured to it from Joplin and couldn't be happier.
Other (FOSS) tools I use for productivity... GUI tools:
- nocodb - a web-based database which can be accessed over API too
- I'm keeping an eye on vikunja.io, hope to have it mature and implement more features regarding project management
- paperless-ngx, make order of your paper-mess.
CLI tools:
- Fish - a very nice and modern shell
- chezmoi - a really nice dotfile manager
- lsd instead of ls, dust instead of du, zoxide instead of cd
- kopia - awesome backup tool. How backup is related to productivity? Disaster recovery ;-)