klammertext-align.el calls string-trim, string-blank-p, and string-empty-p without requiring subr-x. Newer Emacs has that library loaded already; on Emacs 27 -- what Ubuntu 22.04 and Pop!_OS 22.04 ship -- the symbols are void and table alignment fails with "Symbol's function definition is void: string-blank-p". The README now states Emacs 27.1 as the supported floor. (from dev 43a4ce7dea2a)