Linear counterexamples to the fourteenth problem of Hilbert

Following ideas of AʹCampo-Neuen [Indag. Math. (N.S.) 5 (1994) 253–257], we construct linear counterexamples to the fourteenth problem of Hilbert from non-linear counterexamples [D. Daigle, G. Freudenburg, J. Algebra 221 (1999) 528–535; G. Freudenburg, Transform. Groups 5 (2000) 61–71].