@tito666 What doesn't make sense is someone who needs to open 100 tabs all the time even if just 10% will be used. In fact, I think that someone who always need to have hundreds of tabs opened simply has a problem with the closing of tabs.
Those people don't need a browser feature but just learn how to close tabs.

An regarding the other issue, it shouldn't be a problem in 2020.

Using a Chrome extension with Slimjet (GetCRX), I can pack installers for extensions and themes from their Chrome pages. The extension installers so packed will install into Opera. Opera refuses to install the themes, however.