This is what I did and it can be complicated and expensive but for me it was happy wife, happy life. I fulltime and use T-Mobile and have a true unlimited data plan for her phone. It's a higher end smartphone that has an HDMI output on it. She connects the HDMI cable to the TV and then watches Netflix all she wants straight from the phone.
Now the problems....
T-Mobile coverage is decent close to cities but iffy in more rural areas so it may not be the first choice for most RVers. There might be other carriers that have an unlimited plan but usually they are not unlimited LTE (high speed). (Thankfully it hasn't been much of a problem for us as I need to be closer to cities for work, No contracts either so if it doesn't work, no loss).
May need to upgrade phone to a smart one that has a TV out or HDMI output. Even though most phones will tether all plans that I have found will only allow a small amount of data to be tethered so unlimited streaming won't work using the phone as a hot spot, only directly streamed from the phone itself.
If you already have some of the above it may not be a huge initial expense but for a shorter trip it probably isn't worth it.
I do like having the unlimited LTE for more than just streaming as I use it almost exclusively for our internet but I do most of my internet browsing on my phone, and only a few times have I been without coverage.