When the supply of Raspberry Pis was drying up, we started recycling returns to make them work again, but even that would not be sustainable.
There is no real alternative, nothing with a functioning Linux kernel and hardware that doesn’t die because of low/high temperatures or humidity or the like. The Raspberry Pi is engineered to a higher standard.
Only since December 2022, a next-generation Rockchip ARM board is shipping that’s based on Cortex A-76 and has 8K video out, but it is expected to get mainline Linux support only in 6.3.
Raspberry Pi works, the rest is just tinkering. Raspberry Pi supports some important niche economies, whose dependents would also break apart, if they didn’t get them. Medical sector, laboratory analysis, etc, etc.
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What I want to add is that the Raspberry Pi 400 always stayed in stock, and I’ve bought one for my child. So you’re also wrong on that aspect as well.