sc-im Spreadsheets in Your Terminal (github.com)

sc-im is an open-source, ncurses-based spreadsheet calculator for the terminal with a vim-like editing interface. It supports large grids, undo/redo, CSV/TAB/XLSX/ODS import and export, formatting, sorting/filtering, plotting via GNUPlot, and scripting through Lua plus external modules. The project is maintained by a single developer and encourages users to star or donate to support ongoing development.