What is the best? Cursory googling suggests SD cards last ~decades at normal usage [0], and in this context where it's barely accessed, maybe longer?

[0] https://www.sdcard.org/consumers/faq

Probably depends on the quantity of data. If you're talking GB's or TB's of digital data, then maybe "archival grade" DVD's or BluRay's.

https://www.verbatim.com.au/product-category/data-storage/op...

If it's instead just a few short strings of text (eg GH password recovery codes), then you could use physical storage.

eg engrave the codes into something that'll survive extremes (granite?), and keep them in a fire proof safe.

Or something along similar lines. Probably don't engrave into glass though, due to that potentially shattering in some situations.

If you go to bluray.com you probably can read the same only for blu-ray.

Better search for a neutral source.

I wrote some scripts to generate QR codes, then printed them to photo paper.

https://github.com/alexjh/gpg-backup/blob/master/Makefile

Back then I thought that QR codes were a bit of a gimmick but now I'm way more confident that I'll be able to read them in the future.

My choice are 8cm DVDs of decent quality. And inability to quickly overwrite/damage your data is a bonus.

laser print