Reddit mentions of Millenniata Inc. M-DISC 25GB Blu-ray Media - 15 Disc Cake Box

Sorry to hear about your situation, Here is what I can add to the information available here.

A hard drive without power will hold its data for 5 to 7 years, not optimal.

https://en.wikipedia.org/wiki/M-DISC theoretical data retention for 1000 years.

https://www.amazon.com/Archival-Verbatim-M-Disc-Inkjet-Printable/dp/B01B99WWXI/ref=asc_df_B01B99WWXI/?

They make a blu ray version too. https://www.amazon.com/Millenniata-Inc-M-DISC-Blu-ray-Media/dp/B00KGWV6MI

I have never used this, but it looks like a regular, non-organic based disc, just make sure your burner drive has support for it.

As others have said, pair a long lasting disc of your brand choice with a reliable (non youtube imho) cloud based storage. best of luck in your endeavor.

Ah ok, so something like this?
Millenniata Inc. M-DISC 25GB Blu-ray Media - 15 Disc Cake Box https://www.amazon.com/dp/B00KGWV6MI/ref=cm_sw_r_cp_api_i_yQmWCbMXCRK1J

Are there any that you would recommend?

So very, very sorry for your loss. Losing my wife would be my ultimate nightmare and it's got to be so incredibly difficult. Wish I could give you a hug, man.

Whatever method you choose, make sure it's got an offsite component to it—in other words, make sure the data are backed up somewhere that's not your home. That way it's protected in the event of burglary, fire, flood, or anything else that potentially damages or destroys your home.

If it's just ~1500MB of data (or about 1.5GB), then I'd recommend something simple like Dropbox, where you can simply copy the files to a local folder on your computer and it's mirrored up into Dropbox's storage cloud. Alternately, Backblaze might be a little more bulletproof (would be less easy to accidentally delete a file locally and have it deleted out of your backup), and would cost you about $50 a year.

Also, old ways work well. Consider putting the data on archival quality optical media and putting that media in a safety deposit box. Just make sure you pick media that are rated for long-duration archive; cheap CD-Rs or DVD-Rs can "rot" as the phase-change material deteriorates.

I hope you're taking care of yourself. Wishing you and your daughter the best of luck and hoping life is kind to you.

Those are LTH discs, not great for archiving. You want HTL discs like these ($41.80/50-disc spindle): https://www.amazon.com/Verbatim-DataLifePlus-White-Inkjet-Printable/dp/B004477BQQ/

Edit: I was wrong, they're HTL discs which should be good for archiving.

Or these Verbatim branded M-Discs ($66.75/25-disc spindle): https://www.amazon.com/Verbatim-M-Disc-BD-R-Branded-Surface/dp/B011PZALWA/

Or the ones you linked earlier, Milleniata branded M-Discs ($64.13/15-disc spindle): https://www.amazon.com/dp/B00KGWV6MI/

The above three products may or may not all use the same chemistry and manufacturing process. Nobody really knows.