I used to be able to just toss .xmp files here: /Users/<INSERTNAME>/Library/Application Support/Adobe/CameraRaw/Settings. Then ACR would find them and I could use them. It's not working with Photoshop (I access ACR through the filter) 2020 or 2021 (I lost 2019 when I upgraded computers). Anyone else stuck with this?
Update - the above file storage does still work. However, you need to click on the two little overlapping circles to access user presets which are kept in a totally separate place than the default ones.