Avoidance of MITM/in flight for electronic data is best done by not filing electronically (esp., given that if you use one of the tax prep packages, all your tax data flows through them unencrypted on its way to going to the IRS).
Print the forms to paper, sign them, stuff into an envelope, and file via the US Mail (sending certified return receipt if you like).
How exactly is paper filing safer, if those with out of control access are placed in a position to MITM, in such a case, by simply opening the incoming envelopes? I would be even more paranoid about such, not knowing what will happen (also - hopefully transitory) with USPS controls, especially if one places the IRS address on the mail ...
I never said "safer". Your concern was MITM/electronic eavesdropping. Paper avoids all the "electronic eavesdropping" possibilities and the fact that TurboTax (substitute your preferred commercial tax prep. software for "TurboTax") has all your tax data in their database. Although if you use TurboTax "online" version they have your tax data anyway, even if you print and file on paper.
Granted, once the IRS receives the paper, it will eventually be entered into their computer systems, at which point the current illegal access to sensitive data by unelected billionaire lackeys can occur regardless of how the return was filed, so the only angle to avoid that item is to delay filing in hopes that some court case blocks the illegal access from occurring before the deadline arrives. But there's no guarantee there, while the deadline is guaranteed to arrive.
The one item that filing on paper does provide, is a small "protest" as to the amount taken. Electronic is easier for the IRS (by some small measure). If they want that much of my income, I'm making it as hard on them as I can within what's legally allowed.
You should have already frozen your credit. If you haven't, follow these steps. It should take you about 15 minutes.
https://www.nerdwallet.com/article/finance/how-to-freeze-cre...