eSIM malfunction may have damaged the SIM reader

Though omitted from the original problem statement, you know what is wrong here, and have a repair estimate.

Guessing how the hardware failure occurred would involve device access, and the cause of the failure may not be clear even with that access.

I suspect all of the SIM and eSIM issues were all secondary to the failure of the cellular board, or maybe the failure and swelling of the battery, or maybe the iPhone was squeezed.

I'm not aware of an eSIM board, though there is a SIM tray assembly. There is a board that handles cellular communications and a few other details, along with the antennae and related connections located on the bottom of that board. How that board might have failed, or how that board got tangled with the other board or with the chassis, is unclear.

A swollen battery is another potential cause, as well.

SIM and eSIM are but a few bytes of identity data, either identity read from a nanoSIM card, or identity data stored in memory having been read from a QR code or otherwise. Yeah, data can also be written to a nanoSIM, but Apple doesn't store user data on those.

To use two different network providers, your iPhone must be unlocked. Otherwise, both plans must be from the same provider. If a CDMA network provides your first SIM, your second SIM won't support CDMA. Contact your network provider for more information. 

If you have an enterprise or corporate data service plan, check with your company administrator to see if they support this feature.

This may help --> SIM not supported No Service Searching Network Provider Lock… - Apple Community