Greetings,
Perform a reset on the device twice. This will take care of the wireless settings. I responded to a similar question previously. Here is an excerpt that would apply to your situation as well.
The printer has both volatile and non volatile memory. You don't need to worry about the volatile memory since its erased when power is cut.
The non-volatile memory is different.
Canon recommends resetting the printer twice in order to erase the wireless settings if applicable. In addition, this information is encrypted and stored in hexadecimal format. To compromise it, you would need to pull the chip, read it successfully and decrypt the data. To use it, you would need to know the physical location of the network. You would then need to travel there (get close enough) to the network to connect to it. Anything is possible, but the probability is low unless you know the location of the network you were trying to penetrate or compromise. That's a lot of work.
Printed documents stored in non-volatile memory. A couple of things here. Most printers use a circular buffer. Data in, Data out, There is always something stored in the middle. Once again however, someone will need a way to read this information from the memory. It might be encrypted. Its also is not stored in a human readable format. Its going to be in UFRII, PCL, postscript, XML, etc. It might depend on the program they were printing from. Someone with malicious intent might get your taxes (if they haven't been overwritten) or the last 10 recipes from your wife's cookbook, kids book report, etc.
Non-volatile memory cannot be completely erased unless data is written to each and every cel or memory space on the storage. There are standards for securely erasing or wiping data from solid state memory or physical disks. The chances for recovery are diminished or become impossible the more times the storage is over written. For liability purposes Canon has a documented procedure for erasing data. The truth is however, data destruction is not instantaneous. It requires software and time. The steps that a 3rd party would need to take are not worth the time without some guarantee they were going to get something useful. With this knowledge, you can decide the level of risk associated with giving, donating or eWasting your printer.
With this knowledge, you can decide what steps should be taken to dispose of the printer.
*Edited for clarity
~Rick
Bay Area - CA
~R5 C (1.0.6.1) ~RF Trinity, ~RF 100 Macro, ~RF 100~400, ~RF 100~500, +RF 1.4x TC, +Canon Control Ring, BG-R10, 430EX III-RT ~DxO PhotoLab Elite ~DaVinci Resolve ~Windows11 Pro ~ImageClass MF644Cdw/MF656Cdw ~Pixel 8
~CarePaks Are Worth It
