it looks like a good candidate for self adhevise something..not a big fan of glue or tape but some of the new adhesives seem pretty strong (i dont know much about them) it looks like you have a rather large surface area to glue or tape, anyway great idea.
was lookin g to see if they will ship a 10 foot gutter to my house....found these!...lol
https://www.rona.ca/en/cap---k-snap-gutter-end-cap