1.5.11 upgrade - Error: Required PHP extension not found : mcrypt

I am attempting to update from version 1.5.10 to 1.5.11 and am getting the error: Required PHP extension not found : mcrypt
I am on PHP version 7.4. I looked and it seems that 7.4 does not use the mcrypt option. Any suggestions?

I was also going to install the update manually but when I went into the WIKI the last version is 1.5.2. Not sure if the instructions are still valid. If someone can confirm that would be much appreciated.

Thanks!