I had a Beoline 2, and it never worked (used with Beocom 2, 5 and 6000).  It used to disconnect or power off entirely all of the time.  Mine might have been a bad one, but that's all I can tell you. I went back to using my old Beoline 1, which is very old but still works and has never gone wrong.  The phone cables where I live are still the old type though - I'm no expert but I think when we get upgraded to fibre-optic where I live (planned for next year), I'll need to look for another solution. Maybe get two Beocom 5 and two Beoline 1, with one connected to each of your two phone lines?

What was the main difference between the BeoLine 1 and 2? I have VoIP here, am connecting the PSTN line from the BeoLine (1 or 2) to a VoIP ATA adapter which mimics a real phone line then hands it off to a VoIP service (we sell those and have one in house). The reason is i want a phone in each bedroom to look normal (and match other BO items), i dont need things like intercom as the VoIP system already does that (via the ATA adapter)... welcome to reach out to me to learn more about the ATA adapters, there not expensive and means you can remain using your BeoCom over a new internet line (the ATA adapter (small box) would terminate the call over the internet then the BeoLine connects to that).

When the phone company finally upgrade our cables, I may come back and ask you about that ATA adapter then, thanks! The Beoline 1 could manage only one phone line, the Beoline 2 could manage two.  That's the main difference I am aware of.  The Beoline 2 was also USB powered whereas the Beoline 1 requires a mains adapter. If you do buy Beoline 1 make sure you get the full kit - the unit itself, the mains adapter, and the 'Y' adapter which allows you to connect both the mains adapter and the phone cable to it.  The mains adapter is very specific as it has a RJ11 plug.  The same mains adapter is used with Beocom 6000 bases. There is also the Beoline 1 mk2 (not to be confused with the Beoline 2!), which is smaller and a bit easier to wire up. I found both on eBay so you can see what they look like:

Looks line a mine field, i found a compatibility chart for the BeoCom 2 and BeoCom5 and bases, BeoLine US will only with the US BeoCom2, the BeoCom5 will not with it... For me i will need to find a BeoLine EU (Mk2) or BeoLine PSTN (i assume this is the Mk1) (as i prefer to stay away from the BeoLine 2).   I know in the UK when BT did the change over to remove PSTN phone lines, they gave everyone a free ATA adapter so you still have an RJ11 port, however if you want real IP voice then your want one of the below, it needs configuration (its an IP device), this will log in to the VoIP provider and just push everything out the single RJ11 port on it.  Generally its highly flexible as they have to work with almost any phone you connect to the RJ11 port, so normally you can select countries in there so it emulates different countries on the RJ11 phone port.  We are a reseller for this brand, there not super easy to setup but generally are robust, we put them in for clients fax machines, ive never had to revisit one ive installed, they "just work" once configured.  They would have servers, usernames and passwords stored so any factory reset will wipe those out, however as mentioned, ive never had to reset one, ever.... https://www.grandstream.com/products/gateways-and-atas/analog-telephone-adaptors/product/ht801v2