Xl2tpd is as a server and as a client via pppl2tp simulteniously

[CpServiceSpb]

There is Ubuntu 18.04 server x64 with xl2tpd 1.3.15 version is installed as Strongswav 5.9.0.
Xl2tpd is set up as Lns and Lac.
There are 2 "hard" net interfaces: lan and wan with IP from ISP IP pool like 10.38.xx.yy
Internet access can be reached only after establishing connection using pppd plugin pppol2tp.so.
After that ppp0 interface with ISP white static IP is appeared.
That is lac is engaged, the server acts as a client for ISP.
Tunnel is established between the server and ISP bras as I understand.

But for the time there is no ability to establish an incoming l2tp connections to xl2tpd.
That is lns can not be engaged, the server can not act as a server for remote clients.

White static IP provided by IPS, assigned to pppol2tp ppp0 interface, is used for incoming connections at clients side.

So, is it possible, at all the situation, incoming l2tp connections while pppolt2p is used or not ?
If there is, what is neccesary to do additional to get it working ?

P. S.: Incoming packets for 500 and 4500 ports from remote clients are visible by tcpdump at ppp0 as well as outcoming from the server to remote clients at ppp0 during xl2tp incoming connection attempts.
Connections is establishing but not established !