  The two known planets in the planetary system of Teegarden's Star are among
the most Earth-like exoplanets currently known. Revisiting this nearby
planetary system with two planets in the habitable zone aims at a more complete
census of planets around very low-mass stars. A significant number of new
radial velocity measurements from CARMENES, ESPRESSO, MAROON-X, and HPF, as
well as photometry from TESS motivated a deeper search for additional planets.
We confirm and refine the orbital parameters of the two know planets
Teegarden's Star b and c. We also report the detection of a third planet d with
an orbital period of 26.13+-0.04 d and a minimum mass of 0.82+-0.17 M_Earth. A
signal at 96 d is attributed to the stellar rotation period. The interpretation
of a signal at 172 d remains open. The TESS data exclude transiting
short-period planets down to about half an Earth radius. We compare the
planetary system architecture of very low-mass stars. In the currently known
configuration, the planetary system of Teegarden's star is dynamically quite
different from that of TRAPPIST-1, which is more compact, but dynamically
similar to others such as GJ 1002.
