Looking at the delta I found this change (referencing the upstream
commit which was received via upstream stable):

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=dbcf24d153884439dad30484a0e3f02350692e4c

This sounds like LRO should not have been configurable and they
(upstram) fixed that now. And they claim any problem are not theirs...
(at least I read it that way).

    
    Commit a02e8964eaf92 ("virtio-net: ethtool configurable LRO")
    maps LRO to virtio guest offloading features and allows the
    administrator to enable and disable those features via ethtool.
    
    This leads to several issues:
    
    - For a device that doesn't support control guest offloads, the "LRO"
      can't be disabled triggering WARN in dev_disable_lro() when turning
      off LRO or when enabling forwarding bridging etc.
    
    - For a device that supports control guest offloads, the guest
      offloads are disabled in cases of bridging, forwarding etc slowing
      down the traffic.
    
    Fix this by using NETIF_F_GRO_HW instead. Though the spec does not
    guarantee packets to be re-segmented as the original ones,
    we can add that to the spec, possibly with a flag for devices to
    differentiate between GRO and LRO.

    Further, we never advertised LRO historically before a02e8964eaf92
    ("virtio-net: ethtool configurable LRO") and so bridged/forwarded
    configs effectively always relied on virtio receive offloads behaving
    like GRO - thus even if this breaks any configs it is at least not
    a regression.
    
    Fixes: a02e8964eaf92 ("virtio-net: ethtool configurable LRO")

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https://bugs.launchpad.net/bugs/1946185

Title:
  large-receive-offload no more tunable in 5.4.0-89-generic

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