I had my TPF on July 3rd, flew 1,800km (2-ish hour flight) on September 26.
It was fine, and you’ll be fine. I’d ticked off the box for assistance, but didn’t ended up needing it and walked to the gate a-ok on my own.
The biggest thing I was concerned about was being able to bend my knee during the duration of the flight. Luckily, I’m only 5’2, so it was okay, and even going to the bathroom on the plane was fine. As for DVT, it’s not any bigger of a risk than it usually is. Just remember to keep flexing your legs and all the other stuff you’d do to keep the circulation going.
In terms of prep, do as much work as you can now. Bend that knee so it’s used to being in a sitting position, work on keeping your Achilles’ tendon, hamstring and sciatic nerve long and loose, and take anti-inflammatories with you, just in case of the pain.