Apart from screen mirroring and sms that everyone has mentioned the proprietary alternative undeniably has more features. I don't know whether it is phone link or link to windows but one of them has a feature where your phone can be used as a webcam over WiFi. As someone who set up ip webcam on my phone and used obs virtual camera through most of the pandemic's online classes it's quite useful and I'd like to see features like that just work and are not relying on mjpeg and proprietary software on the phone end. Their auto hotspot feature i haven't gotten to work and i think is useless but I'm thankful that i don't have to turn off kde connect when using samsung dex.
apps like https://play.google.com/store/apps/details?id=com.parseus.codecinfo (https://apt.izzysoft.de/fdroid/index/apk/com.parseus.codecinfo) show whether or not you've got it, on my samsung galaxy note 20 ultra I've got software only :(
No user replacable battery, no SD card slot, no headphone jack, i'm guessing that since its a new samsung there's little to none avaliable custom ROMs for it. to be absolutely fair the note 20 ultra I'm using to write this comment is basically the same when it comes to a lack of these things except for the sd card slot.
you can disable paging (swap) i guess apart from launching more things at the same time and letting apps know you have ram for them to cache shit (check app settings some apps do have a how much ram should we use slider like okular the kde pdf viewer) and virtualisation of multiple os's i can't think of much
I've been using a phone without a headphone jack for 3 years now with galaxy buds, if i didn't accidentally break the included usbc headset id be using that instead (even on pc) but i did so now i use the headphone jack on my wireless xbox controller on pc (connected to my pc via usb because my motherboard's audio makes noises when the pc is basically doing anything and echoes my mic into my left ear on windows (not a toggle in software or anything but said problem goes away if i power cycle pc by psu and then boot into linux)) and on phone i get to deal with Bluetooth and if i did have a usbc headset again i wouldn't be able to use it and charge the phone in a practical way (wireless charging is an option but my phone discharges faster than it changes wired (when connected to pc), wireless charging is even slower)
nvidia, i swear most of the issues i experience are nvidia related in some way yeah i know using a GTX 1080 with a i7 12700k isn't like the best idea but when given the options of use said gpu and get reasonable framerates with the games im playing (but get massive headaches when something related to the proprietary linux driver eventually breaks, and it does) or use the igpu and get unplayable framerates (or low res) or unnecessarily buy a newer gpu that isn't that big of a jump in performance for me to justify the price I'm sticking with dealing with nvidia