Most adapters will do 1080p, but very few will go beyond that. If the DeX pad doesnt work for you, I can post an Amazon link to the one 3rd party adapter that did give me ultrawide and higher than 1080.
But the price was only like $5 less than the DeX pad, it still didn't give me usb3 or gigabit ethernet; and there's always the chance that Samsung may change DeX compatibility in the future which (intentionally or not) may create issues with 3rd party adapters. But out of the 6 or so I tried 1080p always worked.
Here is the 3rd party one I used which supported Ultrawide and resolutions beyond 1080p:
https://www.amazon.com/gp/product/B07DZYLVKN/ref=ppx_yo_dt_b_asin_title_o09_s00?ie=UTF8&psc=1
you need an adapter with a USB-C in for power input:
Something like this (but there are a ton others):
https://www.amazon.com/Adapter-Samsung-BBing-Delivery-Nintendo/dp/B07DZYLVKN
I use this hub off Amazon. It's got power passthrough (you can charge and play) and 2 usb ports. https://www.amazon.com/dp/B07DZYLVKN/ref=cm_sw_r_cp_apa_i_.QwQCbQKPZZTJ
USB C to HDMI Adapter for Samsung DeX Station, TOPOINT Type-C Hub HDMI 4K for Nintendo Switch, MacBook Pro 2018 2017 2016 https://www.amazon.com/dp/B07DZYLVKN/ref=cm_sw_r_cp_apa_i_-iOPCbRJ6N9SS
TOPOINT USB C to HDMI Adapter for Samsung DeX Station Type-C Hub 4K for Nintendo Switch, MacBook Pro 2018 2017 2016 https://www.amazon.com/dp/B07DZYLVKN/ref=cm_sw_r_cp_apa_i_g6SGCb0E0E1N5
I use this, and it allows charging.
I heard some people used the below, but haven't used it myself.