I store backups on BluRay and bought a USB BD drive for this reason. I’m not planning on keeping the backups in this format forever, if something better comes out in 10 or 20 years I’ll move to that. I only use the drive once or twice a year, so it should last that long, and there will still be adapters for USB type A then.

My biggest concern is getting the disks. I can walk into my local supermarket and buy a DVD-R or CD-R no issues, but BD-Rs (especially high capacity discs) are hard to find even now.