It's done. Sub-sat/vB fee settings merged into Bitcoin Core v30.0 to be released in October.
https://github.com/bitcoin/bitcoin/pull/33106
In case you cannot wait. Add to bitcoin.conf:
minrelaytxfee=0.00000100
incrementalrelayfee=0.00000100
But mind that not alot software out there that already support sub-sat fees. nostr:npub1hea99yd4xt5tjx8jmjvpfz2g5v7nurdqw7ydwst0ww6vw520prnq6fg9v2 has it in Sparrow Wallet's master branch, probably expected in next release version. Also not alot of bitcoin node will relay sub-sat fee transactions right now or right from the start of v30. For now you might need some luck to get them through to miners.