Update was 2020 feb 19, previous was ~feb 16.
NM tries to establish connection, then drops it.

Service "wicked" works well.

I use kernel from "Stable" repo: 5.5.4-2.1.g813d10d, previous was 5.5.4-1.g119f9ca.
All works well with kernel 5.5.4-1.g119f9ca.
Trying both kernels after update: same mistakes.

Enabling/disabling IPv6 didn't helped.

Some output with dmesg:
trying to establish connection every 15 seconds, then fails.

Code:
[   83.324589] r8169 0000:03:00.0 eth0: Link is Up - 1Gbps/Full - flow control rx/tx
[   83.324606] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
[   83.329432] r8169 0000:03:00.0 eth0: Link is Down
[   83.345166] Generic FE-GE Realtek PHY r8169-300:00: attached PHY driver [Generic FE-GE Realtek PHY] (mii_bus:phy_addr=r8169-300:00, irq=IGNORE)
[   83.469659] r8169 0000:03:00.0 eth0: Link is Down
[   83.505739] NET: Registered protocol family 17
[   89.520812] Generic FE-GE Realtek PHY r8169-300:00: attached PHY driver [Generic FE-GE Realtek PHY] (mii_bus:phy_addr=r8169-300:00, irq=IGNORE)
[   89.650909] r8169 0000:03:00.0 eth0: Link is Down
[  116.387431] r8169 0000:03:00.0 eth0: Link is Up - 1Gbps/Full - flow control rx/tx
[  116.391844] r8169 0000:03:00.0 eth0: Link is Down
[  116.409442] Generic FE-GE Realtek PHY r8169-300:00: attached PHY driver [Generic FE-GE Realtek PHY] (mii_bus:phy_addr=r8169-300:00, irq=IGNORE)
[  116.533230] r8169 0000:03:00.0 eth0: Link is Down
[  122.584872] Generic FE-GE Realtek PHY r8169-300:00: attached PHY driver [Generic FE-GE Realtek PHY] (mii_bus:phy_addr=r8169-300:00, irq=IGNORE)
[  122.717883] r8169 0000:03:00.0 eth0: Link is Down
[  149.353390] r8169 0000:03:00.0 eth0: Link is Up - 1Gbps/Full - flow control rx/tx
[  149.357844] r8169 0000:03:00.0 eth0: Link is Down
[  149.381006] Generic FE-GE Realtek PHY r8169-300:00: attached PHY driver [Generic FE-GE Realtek PHY] (mii_bus:phy_addr=r8169-300:00, irq=IGNORE)
[  149.509838] r8169 0000:03:00.0 eth0: Link is Down
[  155.565024] Generic FE-GE Realtek PHY r8169-300:00: attached PHY driver [Generic FE-GE Realtek PHY] (mii_bus:phy_addr=r8169-300:00, irq=IGNORE)
[  155.694958] r8169 0000:03:00.0 eth0: Link is Down
[  182.478672] r8169 0000:03:00.0 eth0: Link is Up - 1Gbps/Full - flow control rx/tx
[  182.483337] r8169 0000:03:00.0 eth0: Link is Down
[  182.501416] Generic FE-GE Realtek PHY r8169-300:00: attached PHY driver [Generic FE-GE Realtek PHY] (mii_bus:phy_addr=r8169-300:00, irq=IGNORE)
[  182.625673] r8169 0000:03:00.0 eth0: Link is Down
[  188.680872] Generic FE-GE Realtek PHY r8169-300:00: attached PHY driver [Generic FE-GE Realtek PHY] (mii_bus:phy_addr=r8169-300:00, irq=IGNORE)
[  188.818780] r8169 0000:03:00.0 eth0: Link is Down
[  215.902989] r8169 0000:03:00.0 eth0: Link is Up - 1Gbps/Full - flow control rx/tx
[  215.907843] r8169 0000:03:00.0 eth0: Link is Down
[  215.924836] Generic FE-GE Realtek PHY r8169-300:00: attached PHY driver [Generic FE-GE Realtek PHY] (mii_bus:phy_addr=r8169-300:00, irq=IGNORE)
[  216.061182] r8169 0000:03:00.0 eth0: Link is Down
[  222.124917] Generic FE-GE Realtek PHY r8169-300:00: attached PHY driver [Generic FE-GE Realtek PHY] (mii_bus:phy_addr=r8169-300:00, irq=IGNORE)
[  222.260393] r8169 0000:03:00.0 eth0: Link is Down