Link two accounts

I have a long standing Firefox account - this one. I have also recently joined Firefox relay, using a different email - the one I most want to be able to mask - however I am trying to link these two accounts, for many reasons but also because I am trying to add my other email as a backup/recovery to this account, but I keep being denied because it's an 'existing account'. Please help. (Also an unrelated but very unhelpful thing: Mozilla websites, and ONLY Mozilla websites, are currently rendering in plain html and it's *really* confusing and unhelpful. I've killed all my as blockers and it doesn't seem to be any of them. Any advice?)