I think the remove doubles option on blender 2.9 became just Merge Vertices > By Distance? I just wanted to check in to make sure I'm not doing stuff wrong though
Exactly ggabrieljim , the hotkey is now 'M', not 'ALT + M'
You also now have auto merge, right at the top right of the 3D viewport in edit mode, next to options.
In the earlier version of 2.8, the hotkey for merge distance used to be "ALT + M". The newer version of 2.83 and 2.93, the " ALT + M" is no longer applied. The developers changed it to the "M" key.