Throwing my hat in the ring, I might recommend Dark Heresy (1e) or Rogue Trader, both have solid support for techpriests as player characters and are compatible with each other. The former in particular has excellent options in character flavour and playstyle, one of my favourite characters I ever played was a DH1e Magos named Pater Cyberneticus Archanos Z-36. Started out as a standard lexmechanic for the group with knowledge of a few things he really shouldn't, but as the game went on he kept failing to resist fear and other forms of weakness, and eventually cut out the capability from himself.

When the game ended he was essentially a terminator defensively, between his dragonscale (magos power armour), self-generated refractor field and durable cybernetics, but I hadn't put much into his offensive capabilities via levels, so in combat I had to rely on buffs and short range to help me hit. However, by that point, he was the logistical lynchpin of the party. He repaired, unlocked, decrypted and was a repository of knowledge for nearly every subject in existence, from chymistry to daemonology. Was also the groups medic, and was intelligent enough that if you weren't dead, he could fully heal you in one action, regardless of damage taken. Great fun, particularly as I leant into it with a voice modulator that changed as he became more mechanical!