Assuming a password manager is used, even jfav0ohjau4gvncgan19@domain should be OK.
On the other hand, I might just be overthinking it. It could even look suspicious to customer support, or is that again just overthinking?
Also, there already will necessarily be some predictable ones, such as work@domain, although servicename@domain would provide even more possible matches.
Currently I am just going with namesurname.tld. If they already know who I am, it doesn’t show anything extra. If it’s something I don’t want linked to me that easily, I can just give it e-mail on some shared domain, and change it later if needed. Though that removes the easy portability.
I’ll probably have more domains eventually.