[suggestion]

look at vexl.it app, it's p2p marketplace, that uses hash of your mobile number and hashes of numbers from contact list, to find buy/sell offers from people you know/ people from your contacts know.

everything is encrypted and private, until you choose to reveal identity in 1:1 chat.

satoshi labs, company behind 1st hardware wallet Trezor works on that. #p2pFTW

[are these swaps fungible?]

well it depends how far does the tax man want to look.

sideshift collects ip address, crypto addresses, times etc.. (so use good vpn that you pay for in monero or lightning (mullvad, ivpn, no shit like nordvpn)

they respond to law enforcement requests. so if tax man writes them email asking where they sent liquid bitcoin that was swapped from usdt erc20, they will tell on you.

if i had to bring some solution, i can say that if someone used exch.cx which is on belize and doesn't collect shit, and you can request deletion of a swap after its done, you could swap USDT on eth, to XMR , which renders any transactions beyond untraceable, and then you could swap this through them again to lightning.

or directly usdt eth to lightning. just be cautious and i cant recommend anything to you nor anyone, i can just point out what exists. be safe