Copy URL with unicode symbols without percent-encoding in Firefox Methods used on Desktop version don't work. I have both browser.urlbar.decodeURLsOnCopy=true and network.standard-url.escape-utf8=false and URLs are still encoded.
This seems to be an old bug as reported here. I did not find any other bug report that specifically relates to Android for this problem (Edit:OP has created a feature request) 

A url shortner such as Tiny url add-on may be an alternative, till a better solution is found, keeping in mind the reservations of OP in comments