Is Samsung working on a new variant of the Galaxy M55 that it could sell as the Galaxy M55s? It appears so: a Samsung smartphone with the model number SM-M558B was recently certified by the Wi-Fi Alliance.
Samsung has the habit of releasing ‘s' variants of some of its budget phones, but it's not a regular occurence as far as its mid-range phones are concerned. The last memorable one was the Galaxy A52s. The Galaxy A53, Galaxy A54 and Galaxy A55 don't have such a variant, and neither do the Galaxy M52, Galaxy M53, and the Galaxy M54.
However, the model number of this mystery phone is a major hint that a Galaxy M55s could be in the works. The regular Galaxy M55 has the model number SM-M556B, which would make the SM-M558B a higher-end variant.
Unfortunately, except for the Wi-Fi certification, there is no sign of the SM-M558B anywhere, so there's no way of knowing how it will be different from the M55. A faster and/or newer chipset could be one of the upgrades, similar to how the Galaxy A52s had a more powerful Snapdragon chip than the Galaxy A52 and Galaxy A52 5G.
But there's no way of knowing based on just the Wi-Fi certificate, so we will have to wait to get more details on the Samsung SM-M558B.