I am using Maxthon 5.3.8.2100 on the Windows7(64bit) operating system. In the browser identification bar (User Agent), I have the following entry:
Mozilla/5.0 (compatible; Windows NT 6.1; U; WOW64; IA64; en) AppleWebKit/599.0+ (KHTML, like Gecko) Maxthon/5.3.8.2100 Chrome/90.0.4430.212 Safari/537.36 OPR/76.0.4017.123 QupZilla/2.2.60
At the same time, I have this picture in a live broadcast on Youtube:
BUT, if I replace at least one letter in the word "Maxthon" of the UserAgent string, for example, I replace the letter "h" with the letter "N" , then everything works as before, as it should be:
Mozilla/5.0 (compatible; Windows NT 6.1; U; WOW64; IA64; en) AppleWebKit/599.0+ (KHTML, like Gecko) MaxtNon/5.3.8.2100 Chrome/90.0.4430.212 Safari/537.36 OPR/76.0.4017.123 QupZilla/2.2.60
Thus, the obvious reaction of Youtube to the word "Maxthon" is revealed.
P.S.:
I'm currently using this script for Violentmonkey, it very effectively "cuts" ads on Youtube:
https://greasyfork.org/en/scripts/408680-youtube-ad-remover