Ruby 2.6 will work.
You can use bundler to install Jekyll in vendor in project gems. i.e. not a global Jekyll gem.
Then later you can use custom Ruby (I recommend 3) and add it to your PATH (it looks like that’s already set up). The system Ruby and the system gems are frozen since Catalina, so it is more flexible to have a custom Ruby that you upgrade whenever you need
Sorry no new commands to recommend but Michael’s comments above could help.
Your pastebin is public but really vague. Nothing about what failed in Ruby or Jekyll other than maybe ffi_c ?
Another M1 topic including ffi_c Jekyll Installation on Macs w/ARM64 w/o Package Manager