That $4 dev board looks like it might be an esp32 killer, or at least good competition. I was thinking of the esp32-c3 which is also risc-v with wifi and ble. It currently has really great rust support. You can even build the stdlib for it so you don't have to mess with no_std. The bl602 doesn't seem to have rust support yet, but I'm looking forward to more options.
Thanks! It wasn't on the awsome rust embedded github yet, but when I dig in I found it. The bl602 does support wifi, but only 2.4 and I presume at lower rates. It definitely doesn't run linux though. But I wouldn't put it past someone to figure out a way.
Try github[0]. There's a community around this chip, with repos dedicated to collecting the documentation and code the vendor itself wouldn't provide, or would require filling request forms to obtain.
It tends to be like this with Chinese chips, and often times western ones too, unfortunately.
[0] https://pine64.com/product/pineseed-bl602-wifi-ble5-soc/