A Saleae-compatible logic analyzer costs less than $10 and can use the open source Sigrok program. Anyone working with microprocessors and logic levels should have one “just in case”. For $10, there isn’t any other tool that offers as much. It’s also relatively easy to learn, with literally thousands of tutorials. I can understand thinking about buying a decent oscilloscope (at least $200) for a hobbyist, but a logic analyzer is a no-brainer imho. It’s not a replacement for an oscilloscope, but can do things almost impossible to do with an oscilloscope (like capturing an EEPROM SPI traffic and decoding it by stacking the Sigrok decoders)
The original 8 channel, 24MHz Saleae was based on a Cypress CY7C68013A chip Saleae Logic - sigrok programmed with custom USB ID. Unsurprisingly, it got cloned right away and the cloned copies are as functional as the expensive Saleae for a fraction of the cost. The value Saleae offers is in the software. While it is possible to run the original Saleae code on the clones, it’s better to use Sigrok and not violate Saleae’s IP.
Saleae stopped selling the original 8 ch, 24MHz devices years ago, and now only offers much more expensive ones.
Next step up would be a DSLogic DreamSourceLab DSLogic Plus - sigrok, for slightly more than $100. It’s a significantly better device (16 channels, 400MHz sampling, better front end for various logic levels), but for most 3.3V-5V uses, a Saleae clone offers 95% of the functionality for less than 10% of the cost.
A debugger like STLink (also <$10) is another no-brainer. But for me at least, debugger and logic analyzers are complementary, and one needs both.