Override sender address in GMail app for non-Google mailbox

There's a popular 3rd-party mail provider and for some time they don't provide OAuth2 auth scheme and resort to regular password. This mail provider was known to authors of Gmail when OAuth2 was still working and for that reason when you try to setup a new email account in the gmail app it redirects to the non-existent OAuth2 web page (even in flight mode). I thought I found a good workaround: at the beginning enter the wrong domain name and later change it to the correct one. It did help me start receiving emails, but when I try to send some it fails. Presumably I get the "non-local sender" error from the SMTP server (GMail app doesn't display the error details). In the composition dialog there's the dropdown at the top where you select the sender account and there the domain is still wrong. I was unable to find where the account could be renamed. In GMail app itself in "Settings" -> (account name) there's the "Account name" text input, but changing the value there has no effect on email composition: in the dropdown the domain name is still wrong and the emails sending still fails. I think GMail is just designed to use the account name from "accounts on device". From GMail app settings you can navigate to "accounts on device" and there there's no UI to rename the account. Only to delete or to disable sync. Since account renaming isn't possible with built-in UI I want to find an app to do that or help with setting the correct account name from the start, but skipping OAuth2. OnePlus 10t (cph2415), Android 14, GMail 2024.06.23