Whether I use the 3.6, 4.x, or 5.0 mongo emulation, txmongo is incompatible with DocumentDB. PyMongo seems to work just fine on all. Inserts and updates work great, the only issues are find and find_with_cursor. Unfortunately, the error message is not very specific.
{
'ok': 0.0,
'code': 303,
'errmsg': 'Legacy opcodes are not supported',
'operationTime': Timestamp(1682704478, 1)
}