Everything that was luks encrypted is unrecoverable once you overwrite the luks header. Trying to guess the master key takes longer than the lifetime of the universe.

Just make sure that is gone and you are good. If you deleted all partitions and installed another (unencrypted) OS on the drive there is a very good chance the luks headers are gone for good.

Follow the steps here to perform a secure erase that resets the cells and wipes any on-device encryption keys:

https://wiki.archlinux.org/title/Solid_state_drive/Memory_cell_clearing

You can do this from a live-boot environment if you wish. I would very strongly recommend disconnecting ALL other drives before performing this step as the best precaution against accidentally nuking the wrong drive. However if you choose to do this with other drives connected triple check you have the right drive selected before each step.

Secure erase just drops the ssd controllers table of where logical blocks are in the physical memory and trims the disk. Which is good and you should do.

That means a person would have to address the memory directly with flying leads or a bed of nails or something. Or have special software that makes the controller tell them what’s on each physical block and then put that data together into a bunch of files.

If that worries you, do dd if=/dev/urandom of=/dev/ before you secure erase.

Then everything on the drive will be random static before the secure erase drops the block table and trims, so even if someone uses magic power to read the block contents directly they just get to see static.

That has the benefit of speeding up the drive by resetting read fatigue at the expense of one layer of writes which is always worth it.

I think one TRIM cycle should make any data unrecoverable by all but the most determined. Feel free to correct me if i'm wrong though.

It you really care, throw this on a usb stick and sleep well. It replaces to old dban system, which has gone commercial. https://github.com/PartialVolume/shredos.x86_64

@JamesBoeing737MAX Overwrite your LUKS-Header and you're good. After this just format in in ext4 and all is gone.

You don't have to install anything on it, just connect it to a running PC and do a dd if=/dev/zero, that should be enough to get rid of any remnants directly accessible.
Unless you are part of a drug distribution organization, in that case just use a hammer, a microwave and a blowtorch.

What type of SSD? NVMe usually has a special instruction which will reset each whole NAND chip, and usually takes a few seconds. I think SATA does as well, but it's not commonly supported.

You said that:

I am giving away a shitty 128GB SSD, which was used with LUKS 2 for most of it's lifetime.

This leads me to assume that it is not now? Is this the case? If it still has LUK2 on it, you can run cryptsetup-erase on the luks2 container. This won't wipe any unencrypted data, though.

One needs to be careful and avoid block level wipes wherever possible for SSD as this will wear it out quicker. Obviously, if you have sensitive data unencrypted, you may have to. Shred is your friend, here. It works on entire devices as well as individual files. The individual files option is preferable if you the sensitive data is at known locations.

cat /dev/urandom > /dev/your-disk should do it in your case. And in 99% of cases.

I'm assuming when you "reinstalled the OS" you just repartitioned the drive and installed normally without encryption for the person? If that's the case then all your old data is encrypted and will be unrecoverable without your password and the LUKS header.

If however you reinstalled the OS within the already made LUKS partition and are giving them the password (for some reason) then yeah, you wanna secure erase it.

If you were selling on eBay or something I would still recommend a secure erase (they're really quick on SSDs)