The issue that jumps out immediately is that there is no META6.json file, However, there are other problems, as illustrated in this output from my attempt to install:
$ zef install Modular
===> Searching for: Modular
===> Extraction: Failed to find a META6.json file for Modular:ver<0.1.2>:auth<Lucien Grondin> -- failure is likely
===> Testing: Modular:ver<0.1.2>:auth<Lucien Grondin>
===SORRY!=== Error while compiling /home/cbwood/.zef/store/p6-modular.git/990846d44b11998eef4685f8cc7d1648c031cffb/t/basic.t
An exception occurred while evaluating a BEGIN
at /home/cbwood/.zef/store/p6-modular.git/990846d44b11998eef4685f8cc7d1648c031cffb/t/basic.t:1
Exception details:
Dynamic variable @*INC not found
in block at t/basic.t line 1
===> Testing [FAIL]: Modular:ver<0.1.2>:auth<Lucien Grondin>
Aborting due to test failure: Modular:ver<0.1.2>:auth<Lucien Grondin> (use --force-test to override)