Edit: At the end of this message is the modified addon ready to install in 2.93. Uninstall any previous version of the addon and close Blender before installing the new version.
For 2.93 and 3.0, you first download @Harvester version with 2.8 fixes from here:
https://blenderartists.org/t/modular-tree/674043/880
And then you replace the file that is shared here inside “nodes” folder (extract the zip and copy the “tree_parameters_node.py” file inside “nodes” folder of @Harvester version):
https://github.com/MaximeHerpin/modular_tree/issues/269#issuecomment-856719327
Just in case before installing the new version, you uninstall any previous version of the addon listed as Modular Tree or MTree, and close Blender. Then install the modified addon.
If you want to avoid work, here is the file with the modifications for 2.93+:
modular_tree-blender_293_fixes.zip (1.2 MB)