I noticed in the current 8949 generation (Feb 24th), some wallets that are custom or expected to be non custodial, don't show up in the 8949 aggregate non custodial.
They just show up as another type of (apparently) exchange, as a named entity (the name of the wallet), and have no long/short gains checkbox selected in the 8949.
I am unable to check or validate the current wallet type tag (that was set on creation, or after a wallet type change), it doesn't seem to show anywhere in the UI.
In one case, an expected non custodial wallet, has the option to upload a 1099-DA. Changing it to a Rabby type wallet got rid of the 1099-DA upload option, but it still shows up in the 8949 and not aggregated into non custodial.
The wallets that show up on their own in the 8949, in some cases use the wrong wallet name (they were renamed at some point, the 8949 references one of the old names)
You also can't explicitly change an existing wallet to type to "Other", which is an option only at a new wallet creation.