I am seeing the below error when trying to install TinyTex on my 2011 iMac:
tinytex::install_tinytex()
The directory /usr/local/bin is not writable. I recommend that you make it writable. See /usr/local/bin not writable · Issue #24 · rstudio/tinytex · GitHub for more info.
0:86: execution error: User canceled. (-128)
add_link_dir_dir: destination /usr/local/bin not writable, no links from /Users/janesmith/Library/TinyTeX/bin/x86_64-darwinlegacy.
tlmgr: An error has occurred. See above messages. Exiting.
Did you follow the link provided and try the recommended solution? For whatever reason you do not have permission to write to /usr/local/bin which is causing the installation to fail. You need to adjust your permissions. Try following the solution in the link, and let me know if that doesn't solve it.