Download Lütjohann’s 1887 MGH text of the Carmina and the Epistulae, either in .txt/.docx or in .pdf format. You can also download practical inventories of both the correspondence¹ and the complete poetry (including in the letters).
¹ For another inventory, see M.P. Hanaghan, Reading Sidonius’ Epistles, Cambridge 2019, 192-99.
These texts (prepared by Joop van Waarden, S.E.&O.) are mirrored in William Carey’s Latin Library and in Ulrich Harsch’s Bibliotheca Augustana; for Letters Books 8 and 9, also in Perseus (the Carmina and Epistulae 1-7 stemming from Anderson’s Loeb edition).