zsh, nvim, fzf -- These things drive my daily everything. I'd pay if that wasn't all FOSS.
You can pay for free software, but you don't need to.
ohmyzsh: https://opencollective.com/ohmyzsh
nvim: https://neovim.io/ supports donations via bitcoin, Open Collective, and GitHub Sponsors.
fzf: https://github.com/junegunn/fzf supports donation via GitHub Sponsors, PayPal, and buy me a coffee.