Board Game Arena

I've not played many tech tree games. On paper, the concept of tech trees appeals to me. Please suggest some tech trees games I can try on BGA.

I am not quite sure what you mean by "Tech Tree Games". I suspect you mean a special kind of engine building mechanism, with a possible sequence of upgrades a player can unlock?

On BGA you can find for example these engine building games, which as far as I can remember have this mechanism, but I am not 100% sure (roughly sorted by complexity, from least to most):
Roll Through the Ages, 7 Wonders, Gizmos, Jump Drive, Kingscraft, New Frontiers, It's a Wonderful World, The Vale of Eternity, Saint Petersburg, The Oracle of Delphi, Puerto Rico, Yokohama, Apiary, Path of Civilization, Wondrous Creatures, Beyond the Sun, Ark Nova.

Enjoy

Probably the most techtreeish of all tech-tree games is Beyond the Sun.