As far as I know if you want to make LTE/NR modem using srsUE software the only way is to use some SDR hardware. At the same time modem inside my phone is integrated in some kind of connectivity SOC (with WIFI and BT). For example Qualcomm Snapdragon series. I wonder is there any SOC that can be used to run open source LTE/NR stack?
Baseband processor SoCs tend to be heavily proprietary and documentation typically only available under NDA, with dev boards and chips hard to get hold of unless you are a vendor promising high volumes.
I don’t think there is any open source UE implementation for a baseband processor SoC. It would be great if a silicon vendor released sufficient materials to make e.g. srsRAN UE support possible, so maybe persuading one would be the first step.