Follow @Marine she had give you the solution, TWRP is unfoundable OK but recovery-e
https://forum.xda-developers.com/galaxy-tab-s6-lite/how-to/howto-unlock-root-galaxy-tab-s6-lite-t4132289
https://forum.xda-developers.com/t/howto-flash-a-blank-vbmeta.4136509/