Ok, so it looks like the core of the problem is signing SDL2_tff.framework. I see that yours has a Frameworks directory in it, with a FreeType.framework in it. When I downloaded SDL2_tff.framework version 2.20.1, there is no FreeType.framework in it.
So I take it you built your own SDL2_tff? (I haven’t done that.) The code signing seems to be stumbling over FreeType, which is embedded within SDL2_tff. Codesign doesn’t sign recursively by default, so since you’re signing on the command line, use the --deep option to the codesign command for SDL2_tff.
OTOH, if you’re codesigning from Xcode, it doesn’t use the --deep option, so you might try the suggestions from here: https://discourse.libsdl.org/t/code-signing-fails-for-sdl2-ttf/28010