So, what are the alternatives?

There’s tons of similar SBC’s out there from Chinese manufacturers, like Orange Pi, Banana Pi, etc; usually using mediatek RISC-V or rockchip ARM processors. They’re all poorly supported on the software and documentation side though and take more work to get going, which has always been where Raspberry shined- nobody else has made embedded computing so easily accessible with click and go OS options and continuous kernel maintenance.
Probably the only board closest to software parity is the pine64 boards… but it’s still not quite as good.