Note: Even though this is an old known issue not specific to 10.10, I think it becomes much more important now when
MDEV-28632 is about to be pushed into 10.10 main; so I'm marking it as 10.10V1 against the standard procedure. Please feel free to adjust both the marking and the priority after deciding what to do about it.
With explicit_defaults_for_timestamp, if a TIMESTAMP column is defined as NOT NULL without a default value, it still partially retains an implicit (only undeclared) logic and gets a current timestamp value if NULL is attempted to be inserted.
Run with --mysqld=--explicit-defaults-for-timestamp=on