Gem Dragonborn, from Fizban's Treasury of Dragons (p. 11), have the Psionic Mind trait:
You can send telepathic messages to any creature you can see within 30 feet of you. You don’t need to share a language with the creature for it to understand these messages, but it must be able to understand at least one language to comprehend them.
The summon elemental spell from Tasha's Cauldron of Everything (p. 111) says:
[The summoned elemental spirit] obeys your verbal commands (no action required by you).
Can a gem dragonborn use Psionic Mind to telepathically issue commands to a summoned elemental spirit?
I think it hinges on a couple things. One is "verbal". The spell does not say "spoken aloud". You can certainly verbalize in your head without saying anything, I'm doing it now, as I type.
Clearly the elemental understands the gem dragonborn. The question is, do commands have to be spoken aloud to be "issued"?
Obviously, in the end it's up to the GM, but I want to be informed for the discussion.
Best Answer
Yes if you have any kind of reasonable DM.
I am not worrying in this answer about RAW, RAI or RA, other that RAF (rules as fun), and I never do, and would always encourage others to view DND in the same light.
A telepathic character essentially has a new form of communication that isn't standard, so we can't expect it to be covered on all the standard rules. It is little beyond a roleplaying gimmick so to not allow the player to make the most fun uses of things like this is against the spirit of the game and all DMs should be encouraged to allow it.
If I wanted a deaf character who communicates in sign language and my DM was pedantic about verbal communication I would probably be annoyed at them neutering my artistic vision for no reason, and this falls into exactly the same category. As a DM, don't be a killjoy.