Use libre boot website’s info for reference. The Athero cars were the only open source option. They are from the aughties. That is your only option. It is the same for hardware - libre boot stuff with a Core Duo era processor, nothing newer is trusted hardware.

Here’s a good list: https://github.com/morrownr/USB-WiFi/blob/main/home/USB_WiFi_Adapters_that_are_supported_with_Linux_in-kernel_drivers.md

For something relatively fast, I suggest you stick to Intel chipsets, and avoid realtek like the plague. As others mentioned, you can go with Atheros, but your speed will certainly suffer, as well as probably breaking the ability to put the computer to sleep with S3.

I understand you would rather go with 100% FOSS, but this carries trade-offs.

I don’t think they exist. The drivers that don’t load firmware blobs into the WiFi device just come pre-packaged with (probably outdated) firmware blobs. Very few devices work without firmware.

You can add a layer of isolation but hooking your device up to a random access point over ethernet, though the experience certainly won’t be as nice.

I think there are also (incomplete) attempts to write fully open-source firmware for WiFi chips like the ESP32, but I don’t know if anyone ever wrote a fast interconnect for the standard dev boards for that. You may need to set up your own PCB to turn those into a fully open source WiFi chip. Performance will be very limited, of course (10-20mbps) because these IoT oriented boards lack hardware processing.

Not very modern, but this card is also available on Novacustom Laptops