Some questions maybe other users will have too:
Some SSD disks like Samsung’s are self-encrypted and they have a tool to safe delete all content by deleting the main encryption key and creating a new one. Is this safe for real?
Question 2: would filling all the SSD free space with random data delete all old deleted data? This would affect the SSD’s time of life but I think it will work. Is this correct?
There are a few vulnerabilities with self encrypting drives.
Hardware-based full disk encryption - Wikipedia
The deleted key may still be able to be recovered though forensics, depending on how it is deleted.
Most likely using nonfreedom software?
This have to do almost nothing with the questions: most people use closed source hardware and we have to deal with it.
It has everything to do with it since it’s on subject of encryption
which is only proven to be passing its threat model until now to be
secure when implemented as Freedom Software. A few Freedom Software
implementations of encryption software are still passing their threat model.
Using closed source encryption by hard drives is on the same level as
using closed source bitlocker by Windows.
No and recent research was published about how hilariously incompetent SSD firmware is in “deleting” stuff.
No because unlike conventional spinning rust drives SSDs use wear leveling which makes drive zeroing useless and just causes its already shorter (than HDD) lifespan to shrink further.
Since you can’t be sure you deleted stuff on SSDs you should have encrypted it with a strong password beforehand and then conveniently forget the passphrase.