@alkhimov, I've been seeing this problem for months on linux, through multiple browser updates, on both Xubuntu-22.0.4 and Almalinux-9.6. It doesn't happen in Windows. Opera keeps asking me to make it my default browsers, but I won't until this persistent issue is solved.
@leocg Ah, like MS's policy to deliberately remove things people find useful. Whenever the word policy is used, something bad happens and common sense flies out the window.
@leocg I thought maybe someone has already found a solution for it in some form (extension, flag, etc...), I didn't necessarily mean the original setting. But I could have been clearer, that's true.
@burnout426 both about:startpageshared and about:startpage are permitted in the address bar, but not in the command line. Weird. I thought the command line was just telling it an address to go to.