Not to be confused with ChrOpera.
The last version of Opera is 12.18 for Windows and 12.16 for Linux and Mac.
While its age makes it long obsolete for the modern web, one unique feature is that it supports rendering WML pages, and WAP sites will not try to redirect you to the PC site if you use Opera. AFAIK, this is the only PC browser that can do this. While WAP sites are basically extinct now in 2024, if you want to make WAP sites yourself, you can play around with them in Opera.
Not to be confused with ChromEdge.
While not quite "retro" in 2024, Edge is also discontinued and devoured by Chromium like Opera.
Edge was discontinued on March 9, 2021 and replaced by ChromEdge in Windows 10 21H1 for new installations, and the April 2021 (postponed to May 2021 for 1809 and 1803) update (20H2, 2004, 1909, 1903, 1809, 1803) for existing installations. It's possible to extract Edge as a cab package and install it on newer versions of Windows 10 (11 untested), with a script that uses some DISM commands. Though, if you installed the Edge cab, you will need to fight with each subsequent update installed, which will again remove Edge and replace it with ChromEdge. (I did this in July 2022 and it worked back then, so at least it survived longer than the below method)
Another method, reported on Reddit, is simply backing up the folder, although it's reported to not working any more since the 2022-01 security update.
Otter Browser aims to recreate the best aspects of the classic Opera (12.x) UI using Qt5.
-- otter-browser.org
It's a browser made in Qt that supports QtWebKit and QtWebEngine (Chromium) backends.
Development seems to have stalled, as there has not been new releases since weekly440 for over two years.
weekly440 is also the first release without an XP build. The previous release, 1.0.03, is the last release with an XP build.