Thanks Norwid for your kind feedback, 1.4.0-2 is uploaded, addressing the points raised.
pyproject.toml has been reworked: the deprecated license table replaced with a PEP 639 SPDX declaration and license-files, [project.urls] added, wheel dropped from build-system.requires, and the test extra separated from the linting tools. You were right that the empty test override was the real problem. The build now runs the test suite -- 2,199 tests, with Build-Depends covering them. The GUI tests remain excluded because pytest-qt is not packaged in Debian, and debian/rules now says so rather than leaving it unexplained. Thank you for the specifics; they were useful. Regards, Cevin Palmer
