We recently built the Digital O-Scope kit from BangGood in China. It is based on the STM32F ARM processor and includes a nice color LCD. It’s single channel and not very fast but plenty fast enough to look at audio signals. For about $30 and an hour of assembly time (yours) it’s a good deal.
It’s not all easy though. The kit includes both through hole and surface mount parts. There is a major error in the documentation because the surface mount parts are never even mentioned in the assembly instructions. The PCB comes with the the STM32 soldered on but there are a lot more surface mount parts you have to install. These other parts are easy enough to solder by hand so it’s not a major issue. But it is a challenge to look up all the parts one by one from the schematic. If you get one of these kits, start by installing all the SMT parts, its much easier to get them on without working around the other parts.
I did talk to the original maker company and they will fix the documentation. I was impressed with the quick response. Apparently they have a version of the kit with all the SMT parts installed and the documentation in my kit was the wrong version.
I have bought several items from BangGood and have not been disappointed. Usually I’m surprised at the quality. The prices are so low it’s hard to believe on some items. I don’t expect the quality to be good but often it is.
The real pain with shopping via China the lead time. It takes weeks to get some items.