How is it acting up? Maybe you can elaborate a bit more.
A 3 year old phone will definitely have battery problems, so that could be one issue.
Any major Android phones are great nowadays, especially if you have a large budget. Samsung is still a great choice as now they promise 3 years worth of OS upgrades for their flagship lineup and some mid range models.
Without knowing further what you don’t like about your S8, it’s a bit difficult to recommend anything specific.
You're right battery is a big issue. Barely lasts half a day with minimal use and I constantly have to have it on the charger to last a full day.
Aside from that apps such as the swype keyboard guve out total gibberish as auto complete and in having to constantly delete and retype. I always found the apple keyboard much better in this respect.
And occasionally have to reboot the phone as chrome just freezes
Typing enter key to start a new paragraph while typing this message makes the keyboard disappear. Happens on this and other forums.
I swear it wasn't like this before!!!
Yes I still like android and I'd buy another android phone like one plus 8 but android manufacturers obsession with curved screens, which imho add no value at all to the user experience is baffling, plus makes finding a screen protector a real pain / almost impossible.
Also, the price point of a flagship such as the s20 ultra makes the iPhone look cheap!!!