JYETech has released a new 2-channel scope, both kit and asssembled, called the "Wave2". It's more advanced than the DSO150 "Shell", with X-Y display, a function generator, and external triggering. It also has a touch screen and two real scope probes. And it's a good bit more expensive than the Shell. JYETech sells the kit without a battery for US$79 and the assembled unit with battery for US$93, with free shipping in both cases. Here's the Wave2 page on their website with all the specs, manuals and schematics.
It appears the Wave2 is generally in the same speed class as the Shell, but more capable, with more features and easier to use, and of course two channels instead of one. The touch screen is resistive. The firmware will be updatable as it was on the Shell.
Based on my experience with the Shell, I think this should be a well- engineered, well-documented product. Of course you won't be doing microwave work with this type of scope, but my Shell has turned out to be surprisingly useful for things like steppers, servos, audio, and various signalling patterns often involved in small projects, and in many cases you just need to know whether there is activity on a line. But I've always missed that second channel.
You will want the Wave2 to be battery powered. But the shipping regulations on individual LIPO batteries are really strange. In email, JYETech tells me that they can ship the assembled unit with a battery included for a reasonable price, but shipping the kit with a separate battery is far more expensive, and they would need to charge $30 shipping for that. Well, of course nobody is going to pay that when they sell the assembled unit, with battery, for $14 more than the kit alone. So if you want the kit, and a battery, the best option appears to be to order the battery separately from Ebay or AliExpress from sellers who appear to have a way around the regs - about US$9. Everything else needed for battery power is included in the kit, including the charger module, the boost converter and the connector.
Banggood also sells the Wave2, but their price for the kit without battery is currently US$91.99. Not sure what's going on there, but the best price right now appears to be from the manufacturer. If you go to the very bottom of the linked page, you'll see a "Buy Online" button. That will take you to AccuDIY.com, which is JYETech's fulfillment site. They take PayPal and GooglePay.
So this is a low-cost low-speed scope. I converted my DSO150 to battery power, and it's what I use most of the time. But two channels would be nice to have.