Custom ROM becoming useless is a common issue on all Samsung phones. The community has not managed to reverse engineer the proprietary Samsung VoLTE implementation.Unfortunately, it cannot be used. My Samsung is acting weird. I have a lot of network problems. Telfon has no bugs on the original software, it works great. 1.the phone does not want to detect the LTE network, it keeps turning on to 3G. 2. LTE coverage is full, even stronger than 3G in my place of residence. 3. VoLTE doesn't work (my network supports VoLTE on the 800/1800/2300/2600 bands). VoLTE does not work because the phone switches from 4G to 3G network when SMS comes in or someone calls. Unfortunately, despite the "PREFERRED 4G" option selected, it does not come back to this network, even when I have USB Tethering active and I use LTE in my computer. 4.The only way to force LTE is to temporarily select 3G and then 4G, then the phone switches to LTE and stays in this network until even receiving an SMS. This software is missing the "LTE ONLY" option in the network selection. The old Samsung SM-G357FZ which has the original firmware (Android 4.4.4) works with my super SIM card. VoLTE works, the phone behaves normally, it always selects 4G automatically, even though LTE in some location is weaker. It chooses the 3G network only when the 4G network is completely lost for a minute or two. This is how LineageOS should work. 5. There is a huge difference between the original software and Lineageos when I do speed tests. On Lineageos, I fail to achieve more than 40-50Mb / s (never!) And on stock software it is always 90-100Mb / s (T-Mobile Polska network). I tested two Samsung phones, the i9505 and the i9506. Both phones are operational. You have to add in the MENU the option "USE ONLY 4G" and improve VoLTE. Without this, in many European countries it is impossible to use the telephone. In Poland, they began to turn off 2G and 3G networks, UMTS transmitters are disappearing, VoLTE4G and 5G appear instead. Without forcing the bandwidth, LineageOs becomes useless in many countries.