Im mostly tech agnostic but i very much understand whats happening under the hood. If it works for the intended audience or use case then thats where I go.
The RSS splits are absolutely permissionless if you're running your own node and hosting your own files.
If you're not, we'll its no different than having a custodial lightning wallet (it literally is that).
The RSS feed simply has a text file with a tag to a lightning or node address. If you self host your feed (on any server) as well, then everything you are doing is 100% permissionless.
If you're talking about the payment rails being used, thats lightning network. Keysend vs lnaddress vs whatever else is a bitcoin lightning problem, not an rss issue. RSS (or more accurately DeMu) uses both keysend and lnaddress but its a bit of a mixed bag of semi compatibility so admittedly not a perfect situation either.