There are two kinds of Alchemy cards:
Rebalanced Alchemy versions of Standard contain the MTG Arena "A" in-line with the card name. They will also have the MTG Arena "A" as a "foil stamp" at the bottom of the card. Internally, their name is slightly different as well, with an "A-" prefix to indicate that they are the rebalanced version. For example, A-Esika's Chariot is the rebalanced version of Esika's Chariot. This only really matters for things like deck import and export, though; name-a-card effects and other in-game mechanics still refer to the normal name.
Designed-for-digital Alchemy cards also have the "A" stamp. In addition they have a separate expansion symbol for each released set.