There was some kind of correction for uBOL¹, and as a result, my filter no longer works in uBO dev or uBO 1.66.0+ / 1.65.2+:

||filepuma.com/updates3$uritransform=/^\/updates/\/pl\/updates/,_,doc

Now the first character of the URL is detected (which is mainly h):

||filepuma.com/updates3$uritransform=/^(https:\/\/www\.filepuma\.com)(\/updates3)/$1\/pl$2/,_,doc

URL to tests (you should see Polish Ups! Strona nie znaleziona. Nie mogliśmy znaleźć strony, której szukasz.):

https://www.filepuma.com/updates3v2/ID?src=XXX&id=XX&v=X.X.X.X