In case this helps anyone..
A way to work around this is to install Playnite and install the itch.io plugin, and use Playnite to find your itch.io games, etc.
If you want to install all itch.io games you don't have installed, then create a filter in Playnite filtering Library by itch.io and check the "Not installed" box. Then, go down your list and double-click each entry you want to try. That will pop up the install box in the itch.io app and you can install each item there one by one by one by one by one by one by one by one by ........ Note that a fair amount of the games, books, etc are somehow unable to be installed from the app but most of them work.
(Anyone looking at this has probably figured this out by now but..) If when trying to install something the itch.io app gives you an error something like "Too many HTPP connections", try again, because it means the app is hitting the itch.io website too quickly and the request will probably work if you try again.