You will need to have Oblivion installed, fully patched upto version v1.2.0416. If you have GOTY or KOTN it will already be fully patched.You will need to have the latest version of Nehrim downloaded (at time of writing the DE (German version) is at v1.0.9.5 and the EN (English version) is at 1.0.9.1.
After Patch 0's Hotfix 4 broke my previous playthough, I adjusted my mod loadout and started a new game. I didn't want to have to worry about that happening again, but BG3 has only just come out, and we can likely expect an ongoing number of updates from Larian over the next month or two as post-launch bugs are patched, and live service support kicks into full gear.