A mailed tax return cannot be tracked until the IRS starts processing it. There are stacks of unopened mailed tax returns sitting at regional offices waiting for processing to start on them. The IRS has not indicated how soon they will be able to work through the backlog.
See this for the status of current operations:
https://www.irs.gov/newsroom/irs-operations-during-covid-19-mission-critical-functions-continue
