I upgraded iMac [mid 2011] from El Capitan to High Sierra 10.13.6, it loaded Safari 11.2.1. But my MacBook Pro [mid 2012] uploaded High Safari 13.2.1. Safari 13.2.1 accesses more web sites than 11.2.1.
How can I upload Safari 13.2.1 into the iMac?
iMac 27″, macOS 10.13
I vaguely recall that under High Sierra there was at least one "standalone" Safari update, which is perhaps what you're missing. But if it's not offered to you as an update in the app store on your iMac, I'm most likely mistaken.
You might look at this earlier discussion of the topic for help.
Cannot update safari past 11.1.2 on High … - Apple Community
high sierra safari 11.1.2 vs 13.2.1
