So this is kinda silly, but it looks like I have two Trello accounts and I don't know how to log in to one of them.
1) I can log in as elizabethbrough with gmail
2) I can see a board the other me shared with me
3) the other me is called lizzie425
4) I don't know how to log in to lizzie425 - I can't find what email address is associated with this account
5) I need to discover how to log in to lizzie425
6) I would like to learn how to merge these accounts or transfer board ownership
Thanks for all your help
Welcome to the Atlassian Community!
Trello uses Atlassian accounts for identity, and the email address for those is private. If you've lost the email address, there's no way to find out what Atlassian account (or legacy Trello account which will need to be converted to an Atlassian account) is associated with it.
The only thing you can do is ask Atlassian directly. Go to https://trello.com/contact and use the "contact us" link in the last option (the others take you to docs or back here).
They may be ab;e to help you with a merge too, although I'm not sure there's any way to merge Atlassian accounts, it might be just moving some stuff over to your newer account so that you own it, while leaving your old account in the history records.