From some comments i read in the mod page just keep spamming expedition sites until there is an option for it be a holy shrine. Haven't tried it yet but gonna start doing it that way.

Can confirm, aside from Luch site Keep visiting the same site again and again it will eventfully give you the option to turn it into a holy site.

Thank you for your input, I am gonna try that. I have already been to over half of the available expidition sites. Time to spam one in particular

Indeed you just need to spam expeditions on the site you want to become your new holy site and it will eventually becom one !

go to economy view and look for holy site buildings that don't match up with existing religions, so far I've found 3

1. Iceland
2. west Ireland
3. northern Norway
4. Malta