In digital circuits the “frequency” when the lumped model breaks down is determined by the slew-rate (ie. spectral content of the edges), not the bitrate/clock

In digital circuits the “frequency” when the lumped model breaks down is determined by the slew-rate (ie. spectral content of the edges), not the bitrate/clock frequency. In the electronics hobbyist community there are many cases when you can run into that issue head first while just connecting modules together (because the whatever IC on the module has significantly faster slew-rate than you need). Another example are MCUs with somewhat high internal clock rates and their power requirements, even 20-ish year old dsPIC requires somewhat involved supply decoupling topology to work at all (and the quality of decoupling for ESP32 has direct effect on signal quality and how much of RF noise it spews out).