The version of Firefox ESR (91.3.0) on which Tor Browser 11 is based requires macOS 10.12 or above, so you would not be able to update to Tor Browser 11 without first upgrading your version of macOS.
The latest version of Tor Browser that will work with macOS 10.11 is Tor Browser 10.5.10, which you can download from the archive. But I would not recommend using a outdated version of Tor Browser as you would be missing out on important security updates and other updates in general.
While there’s no official Tor Browser for iOS, we recommendOnion Browser, which is open source, uses Tor routing, and is developed by someone who works closely with the Tor Project. However, Apple requires browsers on iOS to use something called Webkit, which prevents Onion Browser from having the same privacy protections as Tor Browser.
You allowed me to have the last version compatible with MacOs 10.11, I thank you.
Thanks to the archives, version 10.5.5 is not usable under El Capitan. Too bad you can’t access archives from the main Tor site.
It’s a shame that Tor Browser’s automatic update doesn’t take the OS version into account, because restarting the software with an incompatibility warning is pretty damn stressful. If there was a checkbox to stop searching for updates, that would be nice.