If it was my phone my first thought would be to replace the charging port assembly. Two of your microphones are located on that part so that should get you fixed up most of the way. The charging port is not paired to the logic board in any way, so there should be no ill effects to replacing it; you definitely won't lose Face ID from changing it. Unfortunately iFixit doesn't have a guide for that repair, but there's a Spanish site called Nadie Me Llama Gallina that has just what you need.
[link|https://www.nadiemellamagallina.com/en/manuales/smartphones-1/apple-5/apple-iphone-xr-894/flex-con-conector-de-carga-7828|Manuales / Apple iPhone XR / Flex with charging connector|new_window=true]
As far as replacement parts, they're available on all the major sites including Amazon, eBay and AliExpress among others. The color of the charging port is supposed to match the phone, so if you want to be correct you should find one that matches, but here's an example from Amazon that would work; they have black, white and gold colors available.
[link|https://www.amazon.com/REPAIR-Charging-Connector-Replacement-iPhone/dp/B07QSF3L9G|Amazon.com: E-REPAIR Charging Port Data Connector Flex Cable Replacement for iPhone XR (Black) : Cell Phones & Accessories|new_window=true]
The rear microphone is mounted on the flash/button flex and again that part can be replaced without problems. Here's the guide for that.
[link|https://www.nadiemellamagallina.com/en/manuales/smartphones-1/apple-5/apple-iphone-xr-894/flex-de-pulsadores-y-flash-7829|Manuales / Apple iPhone XR / Flex push buttons and flash|new_window=true]
Here's an example of where you can buy a replacement part; of course there are many others out there as well.
[link|https://www.amazon.com/REPAIR-Button-Pre-Installed-Bracket-Replacement/dp/B07VCR4HPM?th=1|Amazon.com: E-REPAIR Power Volume Button Silent Switch Flash Light Flex Cable Pre-Installed Metal Bracket Holder Replacement for iPhone XR : Cell Phones & Accessories|new_window=true]
Note that I'm not advocating for Amazon; rather their sites were simply the first ones to come up on a cursory search. You can also support iFixit's repair efforts by purchasing the charging port assembly directly from them; they definitely have a much larger selection of colors available.
[product|IF408-006|iPhone XR Lightning Connector Assembly|new_window=true]
As I mentioned previously, neither of those parts will cause your Face ID to fail. Outside of the Face ID components (the earpiece speaker assembly and the front camera assembly), the only other part on the iPhone XR that's paired is the battery.
Good luck and let us know how it all turns out!