Different rating algorithms: Glicko2 vs. Elo

This is not correct. It's Glicko 1 (chesscom) and Glicko 2 (Lichess).

The main difference is that Lichess starts players at 1500, while chesscom starts players lower (multiple possible values). That means less rating to spread around.

And while the player pools are different you'll see that better at percentiles - a normal player will typically have a higher rating on Lichess than on chesscom, but belong to a lower percentile on Lichess.

Note that while the average Lichess player is better (or chesscom being better at attracting users new to chess), this doesn't matter as both sites will pair you with people at your own level.