@arcanicanis The recommended type is still Proposal, but it is not a hard requirement anymore. Flohmarkt is using Note and I think that makes sense. FEP-0837 shouldn't prohibit this.
That being said, other projects might choose to use attachments. Mitra uses Link attachments that contain references to proposals. For example, my actor object (https://mitra.social/users/silverpill) has this attachment:
{
"href": "https://mitra.social/users/silverpill/proposals/monero:418015bb9ae982a1975da7d79277c270",
"name": "MoneroSubscription",
"rel": [
"payment",
"https://w3id.org/valueflows/Proposal"
],
"type": "Link"
}
The href attribute points to FEP--0837 proposal (or a subscription page, depending on the media type in Accept header).