Should I install Kubuntu 26.04 LTS or the 25.10 interim release?

LTS means Long Term Support, not an older version. Ubuntu-based releases come out every April and October, using a year.month version number. The April release in an even-numbered year, such as 26.04, is an LTS release. Since 26.04 is currently the newest release, it is both the latest version and the LTS version. It will receive support for much longer than 25.10, which is an interim release.

If your priority is always getting the newest features as soon as possible, use the interim releases and upgrade roughly every six months. The trade-off is more frequent upgrade work and a much shorter support window. For a new desktop installation, the LTS release is usually the less troublesome option while still being fully up to date when it launches.

Choose 26.04 unless you specifically want to follow the six-month release cycle. LTS versions generally receive about five years of support, while interim versions are supported for only about nine months. You can still upgrade an LTS installation later; it doesn’t lock you into that version forever. LTS is also more likely to be supported by third-party software installers and documentation.

The download page could explain this more clearly. Right now, 26.04 is the latest release overall, while 25.10 is simply the newest non-LTS release. After the next October release arrives, 26.10 will become the newest interim version, but 26.04 will continue receiving long-term support.