Is Digimon Universe: Appli Monsters Part of the Adventure Timeline?
No, it's not. Digimon (not Appmon) in Appmon are explicitly fictional, though an Agumon leaves its video game at one point. Additionally, the Adventure epilogue shows a world where everyone has Digimon, but in Appmon it's a world much like our own.
(Another note: That 'in the year 2045' thing at the beginning of each episode is quoting a certain AI researcher, not establishing the setting. Appmon is implied to be set in 2016.)