Dmac

Think it depends on what you are doing/trying to accomplish.
For me I got up each morning, grabbed breakfast and logged in for a half day of work.
Logged off at lunch, went and met up with my parents and spent the afternoon/evening doing things with them.
Saved me 2-3 days of PTO and didnt really feel like I missed anything on the cruise.
Now when i cruise with my GF/friends group I wouldnt try it because we are straight into "pool fun" etc by mid-morning.

Working from a ship is better if you don't have specific timelines and scheduled events.  Murphy's law of the seas will apply - when you need the internet the most it will be slow or unavailable at that exact moment.  
If your work is the kind that can be done anytime of day as long as it gets done in a reasonable timeframe then working from a ship is possible.  

I just returned from a cruise on Mariner during which I had to work. My log-in for work requires duel authentication. I tried with only one device, but there simply wasn't enough time to get the code on one device and then login to the other device. Service on the ship can be very slow and the delay in the code being sent/received could be lengthy. I finally broke down and paid for the second device. It was irritating since I was the only one in our party using internet, but it is what it is and I did what I had to do in order to be able to work.

Wife decided to do remote work on the ship.  My understanding is that the wifi strength and consistency really depends on the ship and location.  Here are a couple of takeaways (we were in Alaska):
Switching from one device to another was a mild inconvenience.
The wifi (surf and stream) was just not good enough to support consistent Zoom meetings.  
Downloading was not half as bad as uploading.
Ultimately, she decided, as did I, that vacation is vacation and even a little bit of work took away from our overall experience.  Was not worth it.  And this is coming from two individuals with billing rates in the mid-100.  Really not worth working while on a cruise.

I do the remote work onboard all the time with secure laptop and secondary code authentication. The TOTP Authentication app we use can work without the internet and generates the codes on its own. Was not sure until I tried it but it works disconnected from the network. Not sure about DUO. The only issue I have is slow internet speeds but I am accessing my workstation at the office and my laptop is only serving as a remote terminal so it is not too bad but hopefully will be better when StarLink is installed on all the ships.

Worked from the ship, with varying degrees of success.

With regards to the multiple devices question.  It is possible to switch devices pretty easily as mentioned before.  The issue might be timing.  If you are solo that might be an issue if the timeframe for the code entry is really short.  But if you are traveling with someone you can use their device access for a short switch.  Just make sure that “borrowed” code is not the one you plan on utilizing for the actual meeting, because when they log back in it will kick you off.  
 
As far as real success to do everything it might be a little tricky.  Slow speeds were felt at times.  I found it was easier to do as much as possible off-line and wait to sign in and then link and do everything that requires a connection.  You can connect and let the outbox work while you go get lunch or a drink, LOL.  On Teams if you can do without sharing your camera, that also helps.  I found that Teams on the phone (iPhone) actually did better compared to the laptop.  

DUO can also use a device as a token generator if your IT/Security department allows it.  In this mode it doesn't need to be connected.  See if your DUO is configured to work with alternate authentication.  

I did a little "WFH" trial on Harmony at Thanksgiving so the internet might be "newer/better" than some ships.
I logged my laptop into the ship Wi-Fi and connected, then hotspotted my laptop so that my phone could get Wi-Fi through the laptop.
That allowed the code to come through to the phone to do the VPN.
I generally found it ok, video on Teams was unreliable but audio was fine and email/data was ok if slow.

I was on that sailing. We heard the alpha, but did not notice the ships movement. We did witness the guy that security was after. We had been sitting with our luggage at the schooner bar near the Royal theater side. We were the first groups to go down to line up to get off the ship. Line never moved, so we sat on stools to wait. About a hour later, a man came sprinting thru the bar and ran down the stairs with security officers running after him. A guest ran down the stairs and tackled him at the bottom of the stairs along with security. Guy was handcuffed and taken away. A minute later, they had the passenger that tackled him go with them. Customs officer went to where they were holding the guy. When the guy that tackled him came back, he told us the guy had a warrant out on him. Security guy came by and told us we would be cleared to exit the ship now. I do not understand why they didn’t arrest the guy when he tries to exit the ship, instead of inconveniencing thousands of passengers. After that it still took another hour to get off the ship, resulting in us missing our 11:25 flight home. Before we headed down with our luggage, they kept paging the same guy to go to guest services over and over again. The captain even made the announcement a few times. Don’t know if this was the guy they were looking for.