None (https://www.thevespiary.org/rhodium/Rhodium/pdf/solventfree.kmno4.oxidation.pdf)
(https://www.thevespiary.org/rhodium/Rhodium/pdf/solventfree.kmno4.oxidation.pdf)https://www.thevespiary.org/rhodium/Rhodium/pdf/bd2gbl.pdf (https://www.thevespiary.org/rhodium/Rhodium/pdf/bd2gbl.pdf)
Post 383590 (https://www.thevespiary.org/talk/index.php?topic=11582.msg38359000#msg38359000)
(Rhodium: "Scheme 16 - THF to GBL", Novel Discourse) you find trichloroisocyanuric acid being used in a synthesis of GBL from THF in 19% yield, as well as another reference from Syn Comm, where 1,4-butanediol is oxidized to GBL, presumably in better yield than that.