I have designed a USB PC oscilloscope and so bought some pcb's from JLCPCB.
Its runs about 10MHz and uses a cheap PIC micro and a AD9200 20MHz A2D.
The front end is standard 1m+10pf input.
Voltage range is changed using a 74HC4051.
The PC end is the clever end doing all the display maths and functions plus a fast fourier transform for frequency display.
My PCB design, CAD software is PCBCAD360.