I used the official website (instead of an agency) this time.

I spent almost 2 hours on the website, which arguably makes a good case for paying an agency $40 or so they do the work for you, but if I had to do it again, I think I'd be able to cut the workload down to 20 minutes.

Following are tips

1. Use this site, and create an account tied to your email address (this is optional, but comes in handy if they ask you to fix things)
https://evisa.gov.vn/
2. Make an image of your passport's information page only and make sure it is 2 mb or smaller
3. Take a profile picture of yourself (also make sure it isn't big)
4.Have the following handy for pasting:
a) your address
b) address in VN (I chose the Hilton Garden Inn in Hanoi)
c) employer address and phone number
5. Input your passport details EXACTLY as they show up on the info page (i.e. if your middle name is listed, include it!)
6. The province and ward dropdown fields are a mystery to me, but Chatgpt told me to pick anything I fancied and this worked
7. You do need to pick valid arrival and departure points; I used Noi Bai Airport (HAN) for both
8. Payment: I tried Capital One initially, but this got rejected, so I had to start all over. They accepted my BofA credit card, though

I initially applied on Monday morning, and was rejected because I left out my middle name. The amendment process was quite cumbersome, and I ended up re-inputting everything.

I got tripped up because the email field was grayed out. I needed to click that several times in order to get my previously entered email address to appear.

The short of it is that it's an old school website that was presumably made from several cobbled together databases, so it's quite finicky, but it worked in the end (3 business after my initial submission, in spite of my amendment).