I apologize if this isn’t the correct place to ask this. If not, just point me to the right place, please.
As per the title, I am looking into backing up files - pictures, movies, music, some documents - locally but with little to mo need of having the backup medium hot. I already have a few HDDs lying around but it reaches a point where is becomes bulky and takes up considerable space.
I’ve been thinking of memory cards because they are reasonably affordable and can be stored away easily. But how reliable are those?
I intend to make/save several backup copies.

No, hdd are better but archival dvd/bd is probably better.
That is what I’ve been thinking and I admit I’m partial towards HDDs. Regarding the achival DVD/BD, I see an increasing difficulty to find drives. External drives are flimsy and internal drives have incredibly high prices (€135 to €185). Also, most computer cases nowadays don’t even contemplate bays for it. Maybe it is a dying format?
Anything magnetic is not good for long term powered-off storage.
Agreed but the way things seem to be moving forward, it seems the MDisc (likewise DVD and BlueRay) technology may be moving towards extinction, as the drives are hard to find and expensive to purchase.
I just bought a drive. They are cheap and plentiful. They are literally used for multi-decade archival. They will go extinct eventually but you won’t be alive to witness it.
An internal drive or one of those external drives?
External. I also have two older laptop drives from different machines that converted to External.
If you’re really paranoid you can export the data to different media types including archival dvd and archival tape. Tape is unreasonably expensive for SMB/home use though.