Feeds that go through RSS-Bridge
A feed read through an RSS-Bridge instance can usually be replaced by the engine's own source. Settings → Legacy feeds names the replacement and converts it.
RSS-Bridge is a separate service that turns sites into feeds. If you imported subscriptions that go through one, MicroRSS can read most of them directly instead.
Legacy feeds
Settings → Legacy feeds lists every subscription whose address points at an RSS-Bridge instance, with what the engine would read in its place: the Telegram channel behind a TelegramBridge address, the GitHub releases feed behind a GithubReleaseBridge, a page feed for a CssSelectorBridge, and so on. Convert re-points the subscription to that address and fetches it. Your read state follows: an entry you had read in the bridge feed is read in the new one, matched by its link, and bookmarks are kept.
A feed's settings show the same offer as a banner at the top while the feed still goes through a bridge.
When there is no replacement
A bridge MicroRSS has no source for is marked manual, with a note on what to do. Often the site has a feed of its own; the note names it. For those, edit Feed URL in General by hand.
Pasting a bridge address
A bridge address pasted into Add Feed, or found in an OPML file, is converted on the way in: you subscribe to the native source straight away.