remarkable_find_update_device_id.py

import time
import uuid
import random

import requests

orig_requestid = "f1aa8814-a007-46ad-aede-ae071cacccbe"
orig_sessionid = "2019ed24-e518-4a2c-96d2-af660a7bff97"
orig_appid = "98DA7DF2-4E3E-4744-9DE6-EC931886ABAB"
orig_bootid = "48cfc9fb-e90a-4ace-81aa-2b9eeb928e83"
orig_machineid = "" #censored
orig_oem = "" #censored
req = """<?xml version="1.0" encoding="UTF-8"?>
<request protocol="3.0" version="0.0.4.81" requestid="{{{requestid}}}" sessionid="{{{sessionid}}}" updaterversion="0.4.2" installsource="{installsource}" ismachine="1">
    <os version="zg" platform="reMarkable" sp="0.0.4.81_armv7l" arch="armv7l"></os>
    <app appid="{{{appid}}}" version="0.0.4.81" track="Prod" ap="Prod" bootid="{{{bootid}}}" oem="{oem}" oemversion="2.1.3" alephversion="0.0.4.81" machineid="{machineid}" lang="en-US" board="" hardware_class="" delta_okay="false" nextversion="" brand="" client="" >
        <ping active="1"></ping>
        <updatecheck></updatecheck>
        <event eventtype="3" eventresult="2" previousversion=""></event>
    </app>
</request>"""
url = "https://get-updates.cloud.remarkable.engineering/service/update2"


def get_uuid():
    """Generate a random UUID.

    update_engine/utils.cc just reads this from /proc/sys/kernel/random/uuid
    """
    return str(uuid.uuid4())

def get_oem():
    base = "RM100"
    middle = "743"
    # middle = str(random.randint(500, 800))
    # end = # Censored
    end = str(random.randint(50000, 70000))

    return "-".join([base,middle,end])

while True:
    params = {
        "installsource": "scheduler",  # or "ondemandupdate"
        "requestid": get_uuid(),
        "sessionid": get_uuid(),
        # "appid": get_uuid(),
        # "bootid": get_uuid(),
        "machineid": get_uuid().replace("-", ""),
        "oem": get_oem(),
        # "requestid": orig_requestid,
        # "sessionid": orig_sessionid,
        "appid": orig_appid,
        "bootid": orig_bootid,
        # "machineid": orig_machineid
    }
    resp = requests.post(url, req.format(**params))


    if "noupdate" in resp.text:
        print(f"No update.. OEM: {params['oem']}")
    else:
        print("Found params to get update: ")
        print(params)
        print()
        print(resp.text)

        break

    time.sleep(1)

For anyone passing through here, I made a few tweaks to leezu's awesome script and created a new gist. Working as of September 2020.
Link: https://gist.github.com/chimpdude/2e4673d8554cf3a29856d0d6c85ed20a

still works