I've built high-pass and low-pass filters that are controllable over I2C. Their cut-off frequency can be set over the range of 50Hz to 10Khz

The filters are intended to accompany PlainDAQ which is an open-source module that turns Raspberry pi pico to 4-channel oscilloscope and a single channel function generator.
PlainDAQ Crowdsupply : https://www.crowdsupply.com/kuncu-teknoloji/plaindaq
PlainDAQ Hackaday : https://hackaday.io/project/184104-plaindaq-daq-module-for-raspberry-pi-pico

Here are the general specifications:
✔️Cut-off frequency can be set between 50Hz-10kHz
✔️Buffered Input and output (high-impedance input, low impedance output)
✔️Can be directly powered with PlainDAQ (+/- bipolar supply)
✔️Cool, educational visuals.
✔️Can be controlled with PlainDAQ's GUI.
✔️Compatible with Qwiic connectors.
✔️Uses Digi-pot for cut-off frequency setting.