You might want to consider a PicoScope.
Most PicoScopes, including their most affordable models, use the same software which supports a wide range of serial protocol decoding functions. While the actual supported protocols may depend on hardware (e.g. bandwidth of channels), even the cheapest PicoScopes models support 1-Wire, ARINC 429, CAN & CAN FD, DALI, DCC, DMX512, Ethernet, FlexRay, I²C, I²S, LIN, Manchester, MODBUS, PS/2, SENT, SPI, UART (RS-232 / RS-422 / RS-485), and USB 1.1. You can decode multiple protocols at the same time, the only limitation is the number of input channels you have.
I have PicoScope models 3405D and 2204A and find they both work quite well for serial decoding. While they do not have advanced triggering on serial protocols (which my R&S RTB2004 does have), the PicoScope's memory, search and analysis functions are much more powerful than many oscilloscopes.
The 2204A has a list price os US$ 139, which is less than many software options for bench oscilloscopes!
GL