I have been fishing with a solar powered pontoon boat for over 13 years now.
https://usbackroads.blogspot.com/2012/05/?m=0
In recent years, I have replaced the solar panel with a lighter panel that fits on the rear pontoons. The sealed lead acid battery has been replaced by a small lithium battery that fits into the pontoon pocket.
It works well. I do use it on larger lakes. On smaller lakes I just use my fins.
I believe that it goes faster than a rattlesnake can swim. I might test that out this fall.
As to the boat shown in the article. I did look into converting a houseboat to solar. It is easily done. You want the four trolling motors on the corners of the houseboat. That makes docking a total breeze. Designing a steering system with four motors on the corners that also would have them operate independently as well as in sync would be interesting.
My estimate is that top speed would have been about 5 mph. When you think about it that is plenty fast for "retirement" travel.
I couldn't find a small houseboat, with aluminum pontoons, that would fit on a trailer. Small houseboats are made back east with fiberglass pontoons. That doesn't work on western waters.
I did call a manufacturer and asked if they would build me a houseboat with aluminum pontoons. They said I didn't need aluminum pontoons. Yeah, right.
I thought about converting a party boat with aluminum pontoons, but didn't want to spend the time building a houseboat in retirement and it wasn't my skill set.
After posting this I found this video:
Looks like it would go more than 5 mph!!!