From TheAnalogThing

The Arduino line of microcontrollers are relatively powerful and usually very cheap. For example - even with the current component shortage, you can get purchase a pack of several Arduino Nanos for $8 to $10 each. Historically, these have been $3 to $4 each. You can find out more about Arduino and its ecosystem here:

Arduino for data acquisition

There are several Arduino Oscilloscope projects online that use the Arduino itself as a basic data logger over the computer's USB port, followed by a Software oscilloscope front-end to display this data.

One example of this is nanoscope, an open-source Python-based desktop oscilloscope that works on Linux, Mac, and Windows.

Due to their low cost, Arduino-based oscilloscopes are relatively bandwidth limited (approximately 10,000 samples per second). 10,000 samples per second can comfortably measure sine waves below about 1kHZ, but are not very accurate past that.