After performing a successful connection test on a 4.3U console, this message pops up after agreeing to perform a system update (details in comments) : r/WiiHacks
WAD Manager For Wii 4.3 (Multi Mod Manager) 2018 Tutorial! - YouTube
How to Soft-mod your 4.3u Wii Tutorial Step 3- Before Installing USB loaders - YouTube
How to Softmod Your Wii (4.3) U/E/K/J : 4 Steps - Instructables