Thanks @chazz26FTD for taking the time to create this and post it here... I also did this weeks ago, have checked and all my settings are the same as your screenshots, and the issue continues unabated...
I'm not sure what the difference is between G-Suite and having regular gmail accounts, but I have a couple gmail accounts and use a lot of other things Google provides for free, including google cloud and on very rare occasion some of their other offerings, but also a lot of things relating to the building of websites that require other account setups, and it is all of it gathered together under my g-mail accounts, which re also linked up with each other at google, so I can quickly switch between the two of them...
It also occurred to me earlier today to wonder about the gmail app I've never used but is available for phones and mobile devices, so I installed it on my iPhone and examined the settings... I found that notifications was activated by default, and so I turned it totally off... I had my fingers crossed, but I am finding that the issue continues...