I was thinking updating (back when 5.1.0 was the latest) using ChoiDujourNX was semi-safe because while you never asked N's servers for the 5.1.0 update, it's possible you may have gotten the 5.1.0 update offline from a cartridge that had it.
But right now, AFAIK there are no cartridges out yet with 6.0 FW, so it would be like a giant red flag (imo) to suddenly be on FW 6.0 without your Switch ever asking N's servers for the update officially... because where else could your Switch have gotten the 6.0 update?
Might be worth asking those who got banned when they updated to 6.0 how exactly did they update? (Although this would only be relevant until carts with 6.0 FW built-in come out)