I use two Essential PH+1 phones, both have cell service with Tracfone, one is on AT&T towers and the other on Verizon. Both phones worked great with /e/OS. Recently I needed to move the Sim cards into different phones and found I had two problems.
If I put the Verizon Sim card in a phone with /e/OS already installed it would randomly reboot into recovery, telling me my data my be corrupted and to factory reset if I keep having the problem. Often I had to reboot 3-4 times for the phone to boot and work.
If I put the AT&T Sim card in a phone with /e/OS already installed, it would sometimes loss mobile network data, causing the browser and some apps not to work. A reboot or cycle of Airplane mode got it working again. The status bar always showed a good data connection.
Oddly, the solution to both problems was the same. Always made a backup! Flash the stock firmware, boot recovery, factory reset, power off the phone and install the Sim card. On boot up, run the basic setup, connect to WI-FI and you don’t need to add any accounts. After that installed /e/OS, restore the backup and the phone works great again.
This may help if you’re having problems using /e/OS with any mobile network.