Loot filter, really?

PoE2 is still very early, and nobody knows enough yet to be able to really filter loot effectively. That said, Neversink does have an early "barebones" PoE2 filter available: https://github.com/NeverSinkDev/NeverSink-PoE2litefilter

You'll need to unzip the "Litefilter.filter" file and drop it into your PoE2 game files folder:
For Windows: %userprofile%\Documents\My Games\Path of Exile 2
For Linux: steamapps/compatdata/2694490/pfx/drive_c/users/steamuser/My Documents/My Games/Path of Exile 2
(These instructions are also on the page linked.)

As we learn more about base types and such, you can update the filter yourself directly in the .filter file, or you wait for Neversink to post an updated PoE2 filter on www.filterblade.xyz. I don't think the scripting syntax for loot filters has changed much, so you can probably still refer to https://www.poewiki.net/wiki/Guide:Item_filter_guide for guidance on editing your own loot filter.