What monitor and USB C cable are you using.
It is worth checking the Dex settings on your phone for display settings also.
Regards Obsydian
DAILY DEVICES
ZFold4 [Mobile], Pro5 [Watch], S8 Ultra [Tablet], Book2 i5 [Laptop], Buds Pro2 [Buds] M70A 32/43" [Monitor], Smart Tags+, iPad Mini 5 and iPad Pro 12.9 GEN2 [Tablets], Dell Inspiron Gaming Laptop
HOUSEHOLD DEVICES
ZFlip3 [Mobile], Watch5 [Watch], S7+ [Tablet], QN95A [TV], Q900A [Soundbar], MC28M6075CSM [Microwave], Samsung Level [Speaker], Buds Pro [Buds], iPhone 12, iPad Air 2, Air tags
REGARDS, OBSYDIAN - Car & Tech Evangelist / 2 decades of Samsung Ownership
DAILY: ZFold4, Watch6 Classic, Buds Pro2, 20,000 Power bank, Smart Tags
OFFICE: Book2 Pro i7 [Laptop], M70A 32” [Monitor], Samsung Level [Speaker]
GAMING: M70A 43” [Monitor], Book2 Pro i5, Dell Inspiron G5 [Laptops]
FAMILY: ZFlip4, ZFlip5, Watch6 Classic, Tab S8 Ultra, Tab S7 Plus, Buds Pro2
SPARE: Book2 Pro i5 5G [Laptop], ZFlip3
AV: QN95A [TV], Q900A / SWA900S [Soundbar, Rears],
KITCHEN: MC32K7055 [Microwave], S65DG54M3B1 [Fridge] Jet 75 (Vacuum)
NON-SAMSUNG: iPad Air 2, Air tags, iPad Mini 5, iPad Pro 12.9 GEN2, Phone 12