All of Eevee’s evolutions are in Pokémon Legends: Arceus, and Umberon and Espeon have evolution methods similar to other Pokémon series games.
The only way to evolve Eevee into either Umbreon or Espeon without having access to space-time distortions is to max out their friendship levels during different times during the day.
For Espeon, it must be max level friendship and evolved during the day, which is easy to do with Legends: Arceus since the Pokéball next to Eevee will blink when it is ready to evolve. Just make sure that it is daytime and evolve it, and it will turn into Espeon. The same is true for Umbreon, except it should be evolved at night. You can check your Pokémon’s friendship level at any time with the Friendship Checker.
In order to manipulate time so that you can be sure that your Eevee turns into the correct evolution, there are a few things you can do. Time moves quicker outside of the settlement area, Jubilife Village’s time stands still, and you can always make time go quicker by sleeping in a camp.
Camps allow you to rest for a short period of time, and can easily be used to manipulate time if you want to knock Espeon and Umbreon out of your Pokédex quickly. Camps are located outside of the villages, and you can also use your quarters in Jubilife Village to rest.