This is a supplement to the Archive Team's Deathwatch and Fire Drills. Most of these are just ideas I had jumping around in my head, and they might be subject to changes.
Physically, there might be retro-themed stores with vintage media and hardware in your county of residence. You can also search Craigslist, eBay, Etsy, and Buyee. Digital rarities can be found on archive sites and peer-to-peer networks.
Bandcamp hosts many albums without DRM.
Kirby Manga Mania's localization because I haven't seen it on Bookwalker
Level Up Today instructs youngsters how not to be kidults.
pubnix/tilde servers
I usually discourage mirroring the works of outlaws, though I will make exceptions for evidence that has been covered up, such as Justin Silverman's continuous support for the pedophile Robert Magrann.
dedicated/LCD handhelds
Discord logs with DiscordChatExporter
DLsite was blacklisted by several payment processors, an increasing number of its comics are region-locked, and some of its games have been deleted. Justified for material considered illegal overseas, though the safe-for-work sections (home, soft, comic, app) probably should be duplicated.
Internet Archive because INTERNETARCHIVE.BAK is paused at the moment
itch.io is a mixed bag, though some of its games are mirrored on Internet Archive in case another false takedown happens.
MangaDex keeps glitching on my phone.
Mr. Blinky made custom content for Tamagotchi P's without a Pocket Designer, along with assistants for other models. The dedicated handheld community could suffer a blow if his site went down.
Nintendo games and mods, especially for unsupported hardware such as Satellaview
Onion Farms is the primary competitor of Kiwi Farms. Some of the moderators are hypocrites and the whistleblowers aren't as active as the ones on other forums, though it occasionally comes in handy when Joshua Moon poops the bed again.
Paramount+ delisted The Fairly OddParents: Fairly Odder. It's probably not a big loss, though should we download other streaming exclusives just in case?
plug-and-play consoles not in MAME's database
SocietyGlitch is a private torrent tracker dedicated to rare documents, photos, and videos. While some of its media have been uploaded to Internet Archive and reviewed on Oddity Archive, others could become even more scarce if the primary source disappeared.
software for HTC's Vive series
Valve seems to want you to believe Steam and SteamVR will exist forever.
While some of Yascorn's Tamagotchi comics have digital conversions on DLsite comipo and Internet Archive, other cartoonists' adaptations are out of print and becoming rarer.
yt-dlp gets stuck when trying to process age-restricted videos and some music videos, though it can be supplemented with YouTube Video Finder.
DVDs aren't as sturdy as Blu-Ray Discs, though MakeMKV extracts most of their contents. Menus and galleries can be recorded with a capture device such as the ClonerAlliance Box Pro.
Kiwi Farms documents many online criminals, yet the owner is prone to deleting posts and threads it dislikes. Some of the pages were copied on archive.today, but I just want to be sure.
Laserdisc/LaserActive games with Domesday Duplicator
New arcade games aren't as easy to find online.
The USB-GDROM's translated guide is down, but the original one is still up.
The first Xbox's DLC has become scarce after the closure of the original Xbox Live.
Corruption can be easily mitigated if a partition is formatted with ZFS, btrfs, or HAMMER2.
Peer-to-peer networks such as DC++, BitTorrent, and Kademila can keep files in circulation without depending on a particular server.
rsync clones files as closely as possible, while RAID1 copies an entire device.
A storage unit can guarantee physical media is kept dry and cool.
Android's apps and games are common outside of the Google Play Store and Amazon App Store, though compatibility and emulators are hit-or-miss.
Dreamcast-to-Neo Geo Pocket Color connectivity
ld-decode to prepare non-LaserActive rips for compression
N-Gage games have been uploaded to Internet Archive, though EKA2L1's compatibility is mediocre.
Many online-only games have been adapted to other mediums.
Some plug-and-play consoles and dedicated handhelds still have preliminary status in MAME.
I downloaded The SCP Foundation's collection, but I can't decide which way to share all 6.5 (!) gigabytes.
A few Tamagotchi iD models have firmware dumps.
VMU-to-Dreamcast communications are not sufficiently emulated yet, meaning that the Chao Adventure games can only send properly buffed Chao to the Sonic Adventure duology on real hardware. However, DreamPotato seems to be progressing well.