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.

I’ve had good luck with finding perfectly working internal R/W drives on the local scrap market for cheap. I guess still lots of PCs from that era being junked by offices.
Sealed 25-50 GB BD RW media go for ~$1 per disc when they randomly show up in the surplus store.