tt-rss uses https for schema-less URLs with no fallbacks to plain-text.
i’m not sure how technically correct this is (and i’m not about to start digging in RFCs) but it’s not going to change, because the alternative i.e. tracking all schema-less URLs and requesting them again if SSL connection failed is highly inefficient and overall sounds like a bad idea.
as far as i’m concerned schema-less URLs are a stupid meme invention with no reason to exist. using them when you only serve plain-text http is doubly stupid and pointless, so there’s not going to be any core workarounds for sites like that, especially because the vast majority of websites use SSL anyway and the rest can either get on with the program, go back to fully-qualified URLs as God intended anyway, or simply fuck off.
that said, nobody is going to stop you from adding all sorts of per-feed workarounds using plugins. good luck.