When reading Targum Unkelos for Shnayim Mikra V’echad Targum, how does one pronounce Hashem’s name? Can one say "Adonai" when not not reading Hebrew Tanach or reciting a Bracha?

Targum Unkelus was given at Sinai. Then it was forgotten during the days of Ezra, and was reinstituted when Unkelus the convert said it, as he received it from his Rabbis R’ Eliezer and R’ Yehoshua. Thus it is clear that Hashem’s name "Ado-nai" should be pronounced while reading Shnayim Mikra V’echad Targum. Uttering Hashem’s name in vain is a severe sin of “Thou shalt not take the name of the LORD thy God in vain” (Exodus 20, 6). Hashem’s name should not be uttered unless in praise or thanks giving, and only where obligated, not in vain. It is permitted to say Hashem’s name when saying verses as part of learning or when one teaches others to make a Brachah, but not when mentioning Brachot as part of learning. [מגילה ג. ומהרש"א שם, שו"ע או"ח סימן רטו סעיפים ג, ד, ובמ"ב ס"ק יד, יט, כ].