The LaTeX Package defoldfonts#

This package defines the old font commands \rm, \sf, \tt, \bf, \it, and \sc, which have become obsolete in LaTeX 2ɛ and have been removed from the LaTeX core. It also defines the old KOMA-Script font command \sfb. This can be useful if you are using a class such as the KOMA-Script classes, which do not define the old commands by default, and are also using an old BibTeX style or an old BibTeX package that relies on these commands. However, it should be considered more of a stopgap than a permanent solution. The recommended real solution would be to replace the deprecated commands with, for example, \rmfamily, \sffamily, \ttfamily, \bfseries, \itshape, \scshape, or the corresponding text commands with arguments: \textrm, \textsf, \texttt, \textbf, \textit, \textsc. The new commands can also be combined or nested to combine font attributes, which the old commands do not support.

The package is hosted on Codeberg. Further information can be found in the CTAN catalog entry.