You can use a-z, 0-9 and underscores.
Used by Sticker Importing Apps: https://core.telegram.org/import-stickers
37
Хlара a-z, 0-9 и _ хlосташ лелон мега.
38/37
Deleted Account,
Jun 21, 2021 at 18:34
Хlара a-z, 0-9 и _ хlосташ леиэлон мега.
39/37
Deleted Account,
Jul 19, 2021 at 11:44