I'll start out saying, i'm not very good with this stuff....
I have an Ender 5+.
I had it setup with octoprint and klipper from a guide I found a couple years ago, and it worked OK for me to get klipper installed, working on octoprint, and pressure advance tuned ok ish.
Recently my SD Card became corrupt, and like an idiot I didn't have anything backed up.
So I'm trying to setup the system again from less than scratch and it's kicking my ass.
I've decided i'd like to try Mainsail, as it's interface looks interesting (no other reason)
But I can't for the life of me get it working.
EVERY guide I try and follow seems to fail on the connect between klipper and the printer.
I can flash the klipper firmware successfully, and have updated the port ID in the printer.cfg file, but it always comes back to klipper not being able to see/access the port.
Also, make sure [include mainsail.cfg] is present in your printer.cfg file. Apparently this is important when changing frontends (octoprint -> mainsail).
What hardware are you using for hosting klipper and mainsail? Are you using a pi and mainsail os or a pi with raspberry pi os and kiauh to setup klipper and mainsail? Could you post your klippy.log?
Hardware is a Pi4, 4GB.
I've looked through the log, don't know how to upload file here for you to look through it, and it's too long for character limit. It does indicate issues with the serial port, either permission denied in the case i tried tty0 symlink, or no such file or directory when going strait to the serial/by-id.
I've had varying success, initial try the USB wouldn't show in serial/by-id, I swapped cables and still had no entry. Swapped cables back and tried the next guide/OS, and that gave me the entry in serial/by-id.
also I Tried using the symlink tty0, but that didn't work either.
For the current OS/Setup I think i've messed with too many things, and just need to start over from fresh OS. But I can't think of anything different to try.
Are you still having issues? I just rebuilt my e5p (Klipper, Fluidd, bigtreetech skr mini e3 v3, and new screen) and have been working out the bugs. Everything is working good so far, but still need to find tune the printer.