Yup, Unc0ver works perfectly up to 13.5 (and works on A13). If he‘s on 13.5.1 then there’s no way to jailbreak.The Unck0ver jailbreak should work for you.
Checkra1n
Checkra1n only works up to iPhone X according to the site.
Thanks man! I appreciate it. I'll have to check it out. The 12 comes out soon, but I'm sticking with my iphone 10 xsmax. I stopped downloading updates as soon as Apple started including COVID tracking software - no thanks. Thanks again, I'll let you know if it works!The Unck0ver jailbreak should work for you.