Certain Unicode chars are skipped when avatar initial is chosen

[TwoF1nger]

Using a supported version?

• I have searched searched open and closed issues for duplicates.
• I am using Signal-Desktop as provided by the Signal team, not a 3rd-party package.

Overall summary

I use Enclosed Alphanumeric Supplement letters as first letter in the nickname of some of my contacts, but Signal-Desktop doesn't render it, and shows the next letter instead.

The issue is only in avatars, everywhere else the proper character is shown.

The issue happens both with profile names (chosen by the remote recipient) and nicknames.

(On Android everything works correctly.)

Steps to reproduce

1. Pick a recipient with no profile picture, and a profile name starting with an "extended" Unicode character, or set a nickname similarly.

Expected result

The avatar should show the first letter of the profile name or nickname

Actual result

The second letter is shown instead

Screenshots

Signal version

7.57.0

Operating system

Linux

Version of Signal on your phone

No response

Link to debug log

No response