You can still install old versions going back to the 90s [0]. If you specifically want to update/install a package on a current installation of TeX Live 2025, you just need to run
tlmgr repository set https://ftp.math.utah.edu/pub/tex/historic/systems/texlive/2025/tlnet-final
(You can replace that URL with any of the historic mirrors in [0])
[0]: https://tug.org/historic/