Release 4.2.1

Resolved issues:
#711
#712
#705, by @yurique
dc733d9, by @scrappy
#720, by @bastiaanv

Miscellaneous:
6. Remove extra characters in pop-up.
7. Remove requirement having a NS URL.
8. More logging.

Translations:
Thank you Hung Nguyen Phuteleco!

Co-authored-by: yurique [email protected]
Co-authored-by: Marc G. Fournier [email protected]
Co-authored-by: Bastiaan Verhaar [[email protected]]