NEWSGROUPSERVERS.INFO
The only bundled client here with Usenet search built into the application itself — no separate indexer account to configure. Cross-platform, free with any Newshosting plan.
Eweka's bundled reader, with built-in search. Included free on every Eweka plan and covered by the same Dutch jurisdiction as the spool behind it.
TweakNews' bundled client with integrated search. Note that posting has to be switched on manually in the account dashboard before the reader can use it.
Not a desktop reader — a web-based search that builds custom NZBs you feed to whatever client you already use. Runs anywhere a browser does.
The default answer for most people. Open source, runs on everything including NAS boxes, and every automation tool in the ecosystem speaks to it.
The low-footprint option — a C++ core that idles at a fraction of SABnzbd's memory. The right pick for a Pi, a router or an always-on NAS.
The power-user option — deep header downloading and filtering that the NZB-first clients do not attempt. Windows only, and paid.
A native macOS newsreader that treats Usenet like a browsable place rather than a download queue. The best-looking client here by some distance.