Thanks.
High scores were implemented via LootLocker. I had never used the service before but it was pretty simple. They have an extension available for Unity and Unreal. As well, YYG made an extension for Gamemaker which is what I made this in.
It is using the 'Guest Login' of LootLocker, but they also support first party logins; Steam, Playstation, Xbox etc... The guest login required no addtional setup, it just worked out of the box.
I'll probably use the service more as it the leaderboard service is free if you stay under 10k monthly users.