Hello, I bought a great SSD drive very cheaply, like new, although it was used, I want to install Qubes on it but I don’t know if it is completely safe.
How to make such a disk like this “safer”, something software to manage it and “format” ?
Is it always a new disk for Qubes?
Just format it as usual.
There is a possibility that the SSD firmware is infected but you can’t check it or do anything about it. Either take the risk and use it or not.
If you have time and desire you can rewrite it completely with random data to increase the chance that data of the previous owner will not be available. On the other hand SSDs support TRIM and it should mark that data as free space anyway, it makes it much harder to recover. Also modern SSDs support commands of complete/secure erase, usually it can be done in the official diagnostic tools.
If the old data being still somewhere in the memory is not a problem, then you should use it as you would use new.
Firmware can indeed be modified by previous owner. Maybe you can try to update it using official diagnosing tool of the manufacture.