I login to my Samsung account for SmartThings with a Googlemail email address. I’d like to change it to a gmail address. I’m somewhat nervous however that this will somehow stuff up my SmartThings and or Samsung account. Has anyone recently changed the email address they use for SmartThings and can report it’s not got some nasty side effect?
just change it at https://account.samsung.com and you should be good to go. No nasty side effects!
If you encounter any problems - I was never here and you did not hear from me that there were no nasty side effects LOL 
I’d hold you entirely responsible, naturally. 
Just for info:
…Googlemail and Gmail are the same thing. A Gmail address ending in either @gmail.com or @googlemail.com will deliver emails to the same account. Google uses these two domain names interchangeably…
I know that, that’s the point of the posting. They have the same destination from a Google perspective, but my question related to how SmartThings and Samsung account handled them, since although they are the login “key” to the account and textually different they have the potential to have ripple effects on SmartThings (eg SmartThings backups for hub restore). I’d like to thing there’s a non changing account Id in the background as a primary key, but that’s a design decision and email address could have been used instead.
I wouldn’t - not worth the risk. But… one for the team, right?
I’ve had more than enough messing about with SmartThings of late, keen to avoid any self induced pain. 
I’ve changed e-mail addresses on Samsung accounts in use on SmartThings a number of times without issue. You only ever actually login to Samsung per se and the e-mail address is not the primary key there. Unfortunately I can’t paste an example user object as the triple backquotes have gone haywire in this forum today, but SmartThings uses a UUID to identify users in an internal context, and a ten character ID to identify users in a Samsung context. The e-mail address seems to just be for display purposes.
The only side effect for me was my login name. My samsung account is ancient (from my S3 smart phone). I used my email address as my login name. That account no longer exists so I updated my email. Unfortunately, I can’t change my username so it still has my old email address.
Where is the username, do you mean the nickname? I’m logging in with Google so I assume if I change the Google id (email address) that will also change the login id for Samsung account. My nickname is just my name, which isn’t changing so that won’t be an issue.