In your other comment you laid out potential uses for a "unlocked" ipad
web browser
IoT control panel
video conferencing
photo frame
e-reader
kiosk
The bottom 5 don't really need updates and if Android tablets are anything to go by (looking at you Nexus 10) arguably will work better running on top Apple software instead of whatever half baked garbage gets dumped out of the major distros or "custom rom" makers.
For web browsing, a nine year old tablet will arguably be slow as molasses for the content that would be on the web nine years from now. We have seen this with using old desktop computers to browse the web.
Your argument is pretty weak. There is a whole lot of work to make this happen among not only Apple but the OSS community for almost no gain. The community's time time would be better spent getting fundamentals of Linux Desktop working well so that maybe one day in our lives it really will be the Year of the Linux Desktop™.
Anything connected to a network requires security updates. The bottom five require network connectivity.
> Slow as molasses for the content
An old tablet isn't suitable for general Javascript-impaired web browsing, but there is a wide world of static online/offline content accessible to slow web browsers, as well as bespoke static content delivered via HTTP.
> Whole lot of work.. for almost no gain
The heavy lifting work is in device enablement, but that's a one time cost. Applications exist, work on other devices and are already maintained. Linux iPads would only expand the userbase for those applications.
> We have seen this with using old desktop computers to browse the web.
That's not always the case though. ;)
About 3 years ago I got hold of a fully function dual Xeon system from around 2004 (!).
Only really wanted the case (old workstation, built like a tank) but the system itself still powered on and ran Win7 perfectly fine. Each of the two Xeon cpus was a single core thing (this was from before multi core), ran at ~3Ghz, and used about ~100w.
... and it played back Youtube videos perfectly fine. I think they were 1080p ones too, rather then 720p.
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We've seen that in later years (past this example above), computing power become "good enough" so that even old computers are completely workable more than a decade later.
Later model iPads will probably be the same, "good enough" for years after Apple is done with them.
So you're saying people should just accept their old iPads can't have a meaningful life after iPadOS support ends?
And that's because "Apple doesn't want them to", so that's it. No questions asked, just accept the results?