A few years ago RetroLoader and Start Apps, two items for the C128, were developed. Work has continued in improving them. RetroLoader is now at v0.6.11, and Start Apps is at v0.7.
RetroLoader is a "a browser for the Commodore 128 [that is also] capable of loading and running Commodore 64 programs directly from 128 mode." Start Apps is "a 32K cartridge for Commodore 128 that can contain a set of programs for C64 and C128 modes."
https://www.pastbytes.com/retroloader/
https://github.com/retrocomputacion/startapps
Writing from Lake Tahoe, California,
Robert Bernardo
Fresno Commodore User Group - http://www.dickestel.com/fcug.htm
Southern California Commodore & Amiga Network - http://www.portcommodore.com/sccan
April 26-27 Commodore Los Angeles Super Show 2025 - http://www.portcommodore.com/class