Conversion is now banned from SM LC
Conversion is broken because Porygon can use Z-Conversion to boost all of its stats by one stage. In addition, Conversion allows Porygon to change its type based on the first move in its moveset, so you can essentially end up with an Electric-type Porygon with Thunderbolt, Ice Beam, Recover and Z-Conversion with +1 in every stat. Porygon is literally the only Pokémon in the tier that learns Conversion, and Porygon itself isn't broken, so banning Conversion seems like the best option. This is a similar logic to why Eevium Z was banned instead of Eevee, except that Porygon has a lot more relevance in the LC metagame.

Murkrow is now banned from SM LC
Murkrow basically has the ability to do the same things that got it banned last generation. It can OHKO or 2HKO most of the metagame with a mixed Life Orb set with Brave Bird, Dark Pulse, Sucker Punch, and Heat Wave. It reaches the 19 Speed tier, which means it is only outright outsped by Diglett, Elekid, Voltorb (never used, for good reason), and Choice Scarf users, but these frail Pokémon have to beware Sucker Punch. Murkrow is versatile because it can also viably run Choice Scarf, Eviolite, or Berry Juice sets. Z-Mirror Move is another possibility that SM gives it, which can give it a chance to have a free +2 Attack when it can KO something with it.