To search for available toolchains, run nrfutil toolchain-manager search. The command outputs the list of versions and their status:
$ nrfutil toolchain-manager search
Version Status
v2.6.2 Not installed
v2.4.4 Not installed
v2.6.1 Installed
v2.5.3 Not installed
v2.6.0 Installed
v2.4.3 Not installed
v2.5.2 Not installed
v2.5.1 Not installed
[...]
You can add the --show-all flag to show all available toolchains, including release candidates.