Evolution+GPG: How to encrypt to an alternative address

Hello every one! And please forgive me if this isn’t a good place to ask such as question…

The following case bothers me for quite some time: I have a friend (must be called Bob here for obvious reasons), who used to use his email address bob@AMail.tld for a long time; And during that, he created a PGP key pair that I have signed (and a couple of other peoples too). Now, Bob went on to additionally using bob@BMail.tld as an email address.
So, I get emails from bob@**B**Mail.tld that are signed with a key that only has bob@**A**Mail.tld as its UID. I understand that in general, Bob should now adduid bob@**B**Mail.tld to his key, but for now, he hasn’t. Nonetheless, if I sent an email to bob@**B**Mail.tld encrypted with the bob@**A**Mail.tld public key, bob would still be able to read it, as it is his key (he would probably not even notice, since he uses some programme for all his mails to decrypt).

However, I am not able to tell Evolution (which is my primary mail app, and I think it wouldn’t change in e.g. Thunderbird) to sent an email to bob@**B**Mail.tld that is encrypted with the gpg key of bob@**A**Mail.tld; And from what I have seen, I can’t find an option in Evolution/Seahorse/gpg-cli to add an UID to the key myself (which imho should be there). What do the experienced geekos do in such a case?
Please note: Telling bob to change s.th. is understandably the cleanest solution (and I will probably do so later), but (a) takes a while, (b) might not be possible in other cases and (c) requires me to rely on s.o. else without it being technically necessary, so I would prefer a home-brew solution here!

It’s maybe 8 years since I last used “evolution”.

I just checked with Thunderbird. There, while replying, I can click the “Enigmail” tab near the top of the reply screen. And that allows me to setup “per-recipient” rules. That is, I can define a special rule on which encryption key to use for a particular recipient.

I’m guessing that there is a similar option in Evolution, but you might have to look around to find it.