I understand your frustration but the app has been removed from the app store as far as i know. I havent tried to download it lately though. You still get the link in mobile view of the site.
Tapatalk, the app in question, wasnt worth it imo. Its not much different than most browser apps in mobile view. So not worth installing. It lasted 10 minutes on my phone before i removed it. You are better off just using the phone's browser.
I dont know if another better app will appear in the future though. I expect it will be announced somewhere if it happens. Not sure what extra features you would need for a forum, that arent offered by the default browser options, thats probably why it was so "meh" to me.
With mobile phone browsers, you have 2 views, desktop view or mobile view. With my samsung phone i click on the left bottom button and get the menu, and choose desktop view, so i can see things like thumbs and sigs. Its basically PC view.